kmod: Add an exclude directive to depmod

kmod: Add an exclude directive to depmod

This adds a new configuration directive to depmod that causes
depmod to exclude a give path entry like .debug.

kernel-dbg provides the modules .debug/<module>.ko files and
when installed either directly or when dbg-pkgs are selected
this can cause depmod to fail.

Signed-off-by: Saul Wold <saul.wold@windriver.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>