tcg-mips: Adjust load/store functions for mips64

tcg_out_ldst: using a generic ALIAS_PADD to avoid ifdefs
tcg_out_ld: generates LD or LW
tcg_out_st: generates SD or SW

Tested-by: Aurelien Jarno <aurelien@aurel32.net>
Tested-by: James Hogan <james.hogan@imgtec.com>
Tested-by: YunQiang Su <wzssyqa@gmail.com>
Signed-off-by: Richard Henderson <rth@twiddle.net>
Signed-off-by: Jin Guojie <jinguojie@loongson.cn>
Message-Id: <1483592275-4496-7-git-send-email-jinguojie@loongson.cn>