Add missing custom kernel module targets

Custom kernel module targets are not in the build dependency rule
which cause the copy command of $(my_copy_pairs) fail.
Add it back to $(my_image_copy_files) and remove the prefixed
$(my_staging_dir) from dest of kernel module copy pair.
Then the makefile can handle it well.

Bug: 195888474
Change-Id: Id8cb4c4991905e8bc53ddb5e60e87a36fe43e803
Signed-off-by: Mark-PK Tsai <mark-pk.tsai@mediatek.com>