[AArch64][SVE] Asm: error on unexpected SVE vector register type suffix

This patch fixes an assembler bug that allowed SVE vector registers to contain a
type suffix when not expected. The SVE unpredicated movprfx instruction is the
only instruction affected.

The following are examples of what was previously valid:

    movprfx z0.b, z0.b
    movprfx z0.b, z0.s
    movprfx z0, z0.s

These instructions are now erroneous.

Patch by Cullen Rhodes (c-rhodes)

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D59636

llvm-svn: 357094