cmd/asm: add 128-bit FLDPQ and FSTPQ instructions for arm64

This CL adds assembly support for 128-bit FLDPQ and FSTPQ instructions.

This CL also deletes some wrong pre/post-indexed LDP and STP instructions,
such as {ALDP, C_UAUTO4K, C_NONE, C_NONE, C_PAIR, 74, 8, REGSP, 0, C_XPRE},
because when the offset type is C_UAUTO4K, pre and post don't work.

Change-Id: Ifd901d4440eb06eb9e86c9dd17518749fdf32848
Reviewed-on: https://go-review.googlesource.com/c/go/+/273668


Trust: eric fang <eric.fang@arm.com>
Run-TryBot: eric fang <eric.fang@arm.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: eric fang <eric.fang@arm.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>