[X86][MS-InlineAsm] Add constraint *m for memory access w/ global var

Constraint `*m` should be used when the address of a variable is passed
as a value. And the constraint is missing for MS inline assembly when sth
is written to the address of the variable.

The missing would cause FE delete the definition of the static varible,
and then result in "undefined reference to xxx" issue.

Reviewed By: xiangzhangllvm

Differential Revision: https://reviews.llvm.org/D113096