LoongArch: Set default alignment for functions jumps loops and labels.

LoongArch: Set default alignment for functions jumps loops and labels.

Based on r15-7624, a set of align combinations with better performance
was tested through spec2006.

LA464: -falign-loops=8 -falign-functions=32 -falign-jumps=32 -falign-labels=8
LA664: -falign-loops=16 -falign-functions=16 -falign-jumps=32 -falign-labels=8

gcc/ChangeLog:

	* config/loongarch/loongarch-def.cc
	(la464_align): Add settings for labels.
	(la664_align): Likewise.
	* config/loongarch/loongarch-opts.cc
	(loongarch_target_option_override): Likewise.
	* config/loongarch/loongarch-tune.h
	(struct loongarch_align): Implement the function `label_`.