sd_mod depends on scsi_mod, but due to it being an AutoLoad and not
AutoProbe module, it was not loading when installing the package,
causing unknown symbol errors for sd_mod and anything depending on it.

Closes #14927, #18293, #19351.

Backport of r46176.
Signed-off-by: Jonas Gorski <jogo@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/branches/chaos_calmer@46177 3c298f89-4303-0410-b956-a3cf2f4a3e73