kbuild: allow depmod in cross builds again

depmod from module-init-tools 3.3-pre2 are reported
to work fine in cross build.
depmod from module-init-tools 3.1-pre5 are known to SEGV

Do not workaround older module-init-tools bugs here.
The right fix is for users to upgrade module-init-tools.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>