tools/host_det.sh: fix bashisms

voodoo@hestia:/opt/github/stable-kernel$ ./checkbashisms tools/host_det.sh
script tools/host_det.sh does not appear to be a /bin/sh script
possible bashism in tools/host_det.sh line 6 ('function' is useless):
function warning { echo "! $@" >&2; }
possible bashism in tools/host_det.sh line 7 ('function' is useless):
function error { echo "* $@" >&2; exit 1; }
possible bashism in tools/host_det.sh line 8 ('function' is useless):
function info { echo "+ $@" >&2; }
possible bashism in tools/host_det.sh line 9 ('function' is useless):
function ltrim { echo "$1" | awk '{ gsub(/^[ \t]+/,"", $0); print $0}'; }
possible bashism in tools/host_det.sh line 10 ('function' is useless):
function rtrim { echo "$1" | awk '{ gsub(/[ \t]+$/,"", $0); print $0}'; }
possible bashism in tools/host_det.sh line 11 ('function' is useless):
function trim { local x="$( ltrim "$1")"; x="$( rtrim "$x")"; echo "$x"; }
possible bashism in tools/host_det.sh line 15 ('function' is useless):
function detect_host {
possible bashism in tools/host_det.sh line 35 ('function' is useless):
function redhat_reqs
possible bashism in tools/host_det.sh line 40 ('function' is useless):
function suse_regs
possible bashism in tools/host_det.sh line 93 ('function' is useless):
function debian_regs
possible bashism in tools/host_det.sh line 96 (should be VAR="${VAR}foo"):
        dpkg -l | grep bc >/dev/null || deb_pkgs+="bc "
possible bashism in tools/host_det.sh line 97 (should be VAR="${VAR}foo"):
        dpkg -l | grep build-essential >/dev/null || deb_pkgs+="build-essential "
possible bashism in tools/host_det.sh line 98 (should be VAR="${VAR}foo"):
        dpkg -l | grep device-tree-compiler >/dev/null || deb_pkgs+="device-tree-compiler "
possible bashism in tools/host_det.sh line 99 (should be VAR="${VAR}foo"):
        dpkg -l | grep lsb-release >/dev/null || deb_pkgs+="lsb-release "
possible bashism in tools/host_det.sh line 100 (should be VAR="${VAR}foo"):
        dpkg -l | grep lzma >/dev/null || deb_pkgs+="lzma "
possible bashism in tools/host_det.sh line 101 (should be VAR="${VAR}foo"):
        dpkg -l | grep lzop >/dev/null || deb_pkgs+="lzop "
possible bashism in tools/host_det.sh line 102 (should be VAR="${VAR}foo"):
        dpkg -l | grep fakeroot >/dev/null || deb_pkgs+="fakeroot "
possible bashism in tools/host_det.sh line 108 (should be VAR="${VAR}foo"):
                        deb_pkgs+="libncurses5-dev "
possible bashism in tools/host_det.sh line 124 (should be VAR="${VAR}foo"):
                        dpkg -l | grep uboot-mkimage >/dev/null || deb_pkgs+="uboot-mkimage "
possible bashism in tools/host_det.sh line 127 (should be VAR="${VAR}foo"):
                        dpkg -l | grep u-boot-tools >/dev/null || deb_pkgs+="u-boot-tools "
possible bashism in tools/host_det.sh line 135 (should be 'b = a'):
                if [ "x${cpu_arch}" == "xx86_64" ] ; then
possible bashism in tools/host_det.sh line 139 (should be VAR="${VAR}foo"):
                                dpkg -l | grep ia32-libs >/dev/null || deb_pkgs+="ia32-libs "
possible bashism in tools/host_det.sh line 142 (should be VAR="${VAR}foo"):
                                dpkg -l | grep ia32-libs >/dev/null || deb_pkgs+="ia32-libs "
possible bashism in tools/host_det.sh line 150 (should be 'b = a'):
                                if [ "x" == "x${check_foreign}" ] ; then

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>