x86, PAT: Handle faults cleanly in set_memory_ APIs

Handle faults and do proper cleanups in set_memory_*() functions. In
some cases, these functions were not doing proper free on failure paths.

With the changes to tracking memtype of RAM pages in struct page instead
of pat list, we do not need the changes in commits c5e147. This patch
reverts that change.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20090409212708.653222000@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>