register class tGPRRegClass if the target is thumb1.
This commit fixes a crash that occurs during register allocation which was
triggered when a virtual register defined by an inline-asm instruction had to
be spilled.
rdar://problem/18740489
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221178 91177308-0d34-0410-b5e6-96231b3b80d8