[packages] uboot-envtools-mmc: remove package

Functionality has been added to main uboot-envtools package and that one should
be used instead.

Signed-off-by: Luka Perkov <luka@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/packages@37137 3c298f89-4303-0410-b956-a3cf2f4a3e73
[packages]: update git to v1.8.3.2


git-svn-id: svn://svn.openwrt.org/openwrt/packages@37138 3c298f89-4303-0410-b956-a3cf2f4a3e73