[ARM] Add mrrc/mrrc2 intrinsics and update existing mcrr/mcrr2 intrinsics.

Patch adds intrinsics for mrrc/mrrc2. The
intrinsics for mrrc/mrrc2 return a single
uint64_t to represent two 32 bit values.

The mcrr/mcrr2 intrinsic was changed to
accept a single uint64_t instead of two
32 bit values as the input for consistency.

Differential Revision: http://reviews.llvm.org/D21179

llvm-svn: 272777