kernelscripts: Use make wildcard for file listing

Switch to using make wildcard command instead of invoking
shell for ls to get file listing. This speeds up the
Android build processing time.

Change-Id: I73d092c2a81878671b3c4bed9fe2eb235845b4b8
Signed-off-by: Isaac J. Manjarres <isaacm@codeaurora.org>