aarch64: Re-enable ldp/stp fusion pass

aarch64: Re-enable ldp/stp fusion pass

Since, to the best of my knowledge, all reported regressions related to
the ldp/stp fusion pass have now been fixed, and PGO+LTO bootstrap with
--enable-languages=all is working again with the passes enabled, this
patch turns the passes back on by default, as agreed with Jakub here:

https://gcc.gnu.org/pipermail/gcc-patches/2024-January/642478.html

gcc/ChangeLog:

	* config/aarch64/aarch64.opt (-mearly-ldp-fusion): Set default
	to 1.
	(-mlate-ldp-fusion): Likewise.