[msp430] Only support the 'm' inline assembly memory constraint. NFC.

Summary:
MSP430 doesn't seem to have any additional constraints. Therefore remove
the target hook.

No functional change intended.

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D8208


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@235003 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed