aarch64: Remove redundant feature requirements

aarch64: Remove redundant feature requirements

Many instructions explicitly specified SVE/SVE2/SME/SME2 as a required
feature when it was already implied by another required feature (at
least while the SME->SVE2 implication is retained internally).  These
redundant features were used to determine both the valid symbol names
for immediate operands, and the choice of error message for invalid
movprfx sequences.  Those two scenarios no longer use architecture
features, so the redundant features are now truly redundant.