[asm matcher] Fix incorrect assertion when there are exactly 32 SubtargetFeatures

Summary:
The minimal type needs to hold a value of '1ULL << 31' but
getMinimalTypeForRange() is called with a value of '1ULL << 32'.

This patch will also reduce the size of the matcher table when there are 8
or 16 SubtargetFeatures.

Also added a dump of the SubtargetFeatures to the -debug output and corrected getMinimalTypeInRange() to consider 0xffffffffull to be a 32-bit value.

The testcase is that no existing code is broken and that LLVM still successfully
compiles after adding MIPS64r6 CodeGen support.

Reviewers: rafael

Reviewed By: rafael

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D3787