build: strip debug symbols from installed kernel modules

Debug symbols in installed kernel modules consume space
in the target filesystem, so strip them. Modules with
debug symbols should be present in the KERNEL_OBJ
location for debug purposes. 

(cherry picked from commit bb77a75767f5dbb7327ab05f4ec4462b6ad62b10)
CRs-fixed: 400053
Signed-off-by: Nagender Telkar <ntelkar@codeaurora.org>

Change-Id: I4353e3733455e01cbe97c023d36b9bd3b7b8adf2
Signed-off-by: Neha Pandey <nehap@codeaurora.org>