kernel_headers: Disable headers matching

Disable matching of existing and generated gen_headers*.bp files.
This is done to allow some uapi headers to be added to camera
techpack.

Change-Id: I1b6b639015f3672a3e9daa9b2a1444e952ed4ac1
Signed-off-by: Rishabh Bhatnagar <rishabhb@codeaurora.org>