i386: Remove REG_OK_FOR_INDEX/REG_OK_FOR_BASE and their derivatives

i386: Remove REG_OK_FOR_INDEX/REG_OK_FOR_BASE and their derivatives

x86 was converted to TARGET_LEGITIMATE_ADDRESS_P long ago.  Remove
remnants of the conversion.  Also, cleanup the remaining macros a bit
by introducing INDEX_REGNO_P macro.

No functional change.

gcc/ChangeLog:

2023-04-21  Uroš Bizjak  <ubizjak@gmail.com>

	* config/i386/i386.h (REG_OK_FOR_INDEX_P, REG_OK_FOR_BASE_P): Remove.
	(REG_OK_FOR_INDEX_NONSTRICT_P,  REG_OK_FOR_BASE_NONSTRICT_P): Ditto.
	(REG_OK_FOR_INDEX_STRICT_P, REG_OK_FOR_BASE_STRICT_P): Ditto.

	(FIRST_INDEX_REG, LAST_INDEX_REG): New defines.
	(LEGACY_INDEX_REG_P, LEGACY_INDEX_REGNO_P): New macros.
	(INDEX_REG_P, INDEX_REGNO_P): Ditto.

	(REGNO_OK_FOR_INDEX_P): Use INDEX_REGNO_P predicates.

	(REGNO_OK_FOR_INDEX_NONSTRICT_P): New macro.
	(EG_OK_FOR_BASE_NONSTRICT_P): Ditto.

	* config/i386/predicates.md (index_register_operand):
	Use REGNO_OK_FOR_INDEX_P and REGNO_OK_FOR_INDEX_NONSTRICT_P macros.

	* config/i386/i386.cc (ix86_legitimate_address_p): Use
	REGNO_OK_FOR_BASE_P, REGNO_OK_FOR_BASE_NONSTRICT_P,
	REGNO_OK_FOR_INDEX_P and REGNO_OK_FOR_INDEX_NONSTRICT_P macros.