Surface: Fix gralloc flags conflicting values.

Due to some custom code, unwanted flags (HW) got added with SW flags.
Restrict the flags to custom ones.

Change-Id: I2ab1c75eef4d6d16f0dd7d43aff3c7377486801a
(cherry picked from commit d9b9e1510418e5babf54f34ed8a81cbc368f521e)
(cherry picked from commit 947e0802d55a70aef4c32875f4ddfd2c30576bce)
(cherry picked from commit 4d3419b9185e8f57ff811cf7b14782902c66172f)

Conflicts:
	libs/gui/Android.mk
	libs/gui/Surface.cpp