xtensa: Remove TARGET_PROMOTE_PROTOTYPES

xtensa: Remove TARGET_PROMOTE_PROTOTYPES

xtensa ABI requires sign extension of signed 8/16-bit arguments to 32
bits and zero extension of unsigned 8/16-bit arguments to 32 bits.
TARGET_PROMOTE_PROTOTYPES is an optimization, not an ABI requirement.
Remove TARGET_PROMOTE_PROTOTYPES and define xtensa_promote_function_mode
to properly extend 8/16-bit arguments to 32 bits.

gcc/

	PR target/120888
	* config/xtensa/xtensa.cc (xtensa_promote_function_mode): New.
	(TARGET_PROMOTE_FUNCTION_MODE): Use.
	(TARGET_PROMOTE_PROTOTYPES): Removed.

gcc/testsuite/

	PR target/120888
	* gcc.target/xtensa/pr120888-1.c: New test.
	* gcc.target/xtensa/pr120888-2.c: Likewise.

Signed-off-by: H.J. Lu <hjl.tools@gmail.com>