omap4xxx: add flag to allow custom libion

Due to kernel changes I need to stop the omap4xxx/libion via
BOARD_USES_CUSTOM_LIBION flag and instead use a custom libion
in my device trees.

Change-Id: Ic48e8c51456c76dfd9bca00cb59581deb2cfc510
Signed-off-by: Hashcode <hashcode0f@gmail.com>
(cherry picked from commit de825f2f08fad153116807ea18002e4590bd71bb)
omap4xxx: add flag to allow custom domx

Make it possible for a device to provide its own TI domx
by setting the BOARD_USE_TI_CUSTOM_DOMX flag and including
the domx-headers with TARGET_SPECIFIC_HEADER_PATH.

This replaces "[1/3] omap4xxx: Allow custom DOMX source instead of
Google DOMX default" from cm-10.{1,2} which made it necessary to
also patch frameworks/{av,base}. This is no longer needed when
using TARGET_SPECIFIC_HEADER_PATH to inject the domx-headers.

Change-Id: I09b116fb722ec7f77c5a4b1b4b4138bdd11c6dd6
Merge remote-tracking branch 'upstream/cm-12.0' into cm-12.0