build: Relax Cortex CFLAGS

 * Always set march=armv7-a
 * Use mtune instead of mcpu. Bad code is generated on A15 otherwise.

Change-Id: Idf8ced8eb0e9d3d4676ca8ec69bf56aed5533bf4
build: add strip on kernel modules

kernel modules are huge for prima wlan and we need to strip them
unstriped size 40mb
striped size 2mb

Change-Id: Iefd572732cad0a6f608439618673068a3586fcd5
kernel: Ignore errors with module building

Let kernel fully disable loadable modules

Change-Id: Ia37ec927b092c041ee4c68bf9fd0f28b7339c8ca