ion: Handle the memory mapping correctly on x86

ion: Handle the memory mapping correctly on x86

This patch modifies the ion page pool code to address
limitation in x86 PAT. When one physical page is mapped
to multiple virtual pages, the same cache policy
should be used. Add set_memory_wc/uc call to avoid aliases.
If not, all mappings will be cached(write back).

Change-Id: I98ee8902df0c80135dddfa998c4ca4c2bb44e40e
Signed-off-by: Zhebin Jin <zhebin.jin@intel.com>
Signed-off-by: Vinil Cheeramvelil <vinil.cheeramvelil@intel.com>
(cherry picked from commit 6db47cc7e2f1d8dd8fc84912202ed749d6781a76)

Conflicts:
	drivers/staging/android/ion/Kconfig
	drivers/staging/android/ion/ion_priv.h