[PowerPC] Add Sema checks for MMA types

The use of the new types introduced for PowerPC MMA instructions needs to be restricted.
We add a PowerPC function checking that the given type is valid in a context in which we don't allow MMA types.
This function is called from various places in Sema where we want to prevent the use of these types.

Differential Revision: https://reviews.llvm.org/D82035