x86: change /dev/console to tty to fix job control

Job control is turned off because it cannot obtain controlling terminal on
/dev/console, so it is impossible to do any job control operation behind
real x86 device (keyboard+monitor or virtualized).

This patch switches /dev/console to tty devices for ash on x86 generic target.

Signed-off-by: Jiri Slachta <slachta@cesnet.cz>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37693 3c298f89-4303-0410-b956-a3cf2f4a3e73