Introduce LEGACY_SSE_REGNO_P predicate to simplify a couple of places.

No functional changes.

2021-11-17  Uroš Bizjak  <ubizjak@gmail.com>

gcc/ChangeLog:

    * config/i386/i386.h (LEGACY_SSE_REGNO_P): New predicate.
    (SSE_REGNO_P): Use LEGACY_SSE_REGNO_P predicate.
    * config/i386/i386.c (zero_all_vector_registers):
    Use LEGACY_SSE_REGNO_P predicate.
    (ix86_register_priority): Use REX_INT_REGNO_P, REX_SSE_REGNO_P
    and EXT_REG_SSE_REGNO_P predicates.
    (ix86_hard_regno_call_part_clobbered): Use REX_SSE_REGNO_P
    and LEGACY_SSE_REGNO_P predicates.

Bootstrapped and regression tested on x86_64-linux-gnu {,-m32}.

Pushed to master.

Uros.