x86, pat: Preparatory changes in pat.c for bigger rbtree change

Minor changes in pat.c to cleanup code and make it smoother to introduce
bigger rbtree only change in the following patch. The changes are cleaup
only and should not have any functional impact.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <20100210195909.792781000@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>