gcc: xtensa: add XCHAL_HAVE_{CLAMPS,DEPBITS,EXCLUSIVE,XEA3} to dynconfig

gcc: xtensa: add XCHAL_HAVE_{CLAMPS,DEPBITS,EXCLUSIVE,XEA3} to dynconfig

gcc/
	* config/xtensa/xtensa-dynconfig.cc (xtensa_get_config_v2)
	(xtensa_get_config_v3): New functions.

include/
	* xtensa-dynconfig.h (xtensa_config_v3): New struct.
	(xtensa_get_config_v3): New declaration.
	(XCHAL_HAVE_CLAMPS, XCHAL_HAVE_DEPBITS, XCHAL_HAVE_EXCLUSIVE)
	(XCHAL_HAVE_XEA3, XTENSA_CONFIG_V3_ENTRY_LIST): New definitions.
	(XTENSA_CONFIG_INSTANCE_LIST): Add xtensa_config_v3 instance.
	(XTENSA_CONFIG_ENTRY_LIST): Add XTENSA_CONFIG_V3_ENTRY_LIST.