Don't inflate register classes used by inline asm.

Don't inflate register classes used by inline asm.

The constraints are represented by the register class of the original
virtual register created for the inline asm. If the register class were
included in the operand descriptor, we might be able to do this.

For now, just give up on regclass inflation when inline asm is involved.

No test case, this bug hasn't happened yet.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@134226 91177308-0d34-0410-b5e6-96231b3b80d8