arm64: msac: Add handwritten versions of msac_decode_bool functions

GCC                     Cortex A53   A72   A73
msac_decode_bool_c:           29.9  17.9  23.2
msac_decode_bool_neon:        27.4  15.3  20.4
msac_decode_bool_adapt_c:     49.2  26.8  31.0
msac_decode_bool_adapt_neon:  38.2  22.2  25.4
msac_decode_bool_equi_c:      26.6  16.8  19.4
msac_decode_bool_equi_neon:   23.9  13.7  15.7

Clang                   Cortex A53   A72   A73
msac_decode_bool_c:           28.0  16.4  23.1
msac_decode_bool_neon:        26.9  14.6  21.0
msac_decode_bool_adapt_c:     46.8  25.1  31.4
msac_decode_bool_adapt_neon:  36.2  19.0  26.2
msac_decode_bool_equi_c:      23.7  13.4  18.8
msac_decode_bool_equi_neon:   23.7  11.3  14.2

This is as fast as, or faster than, what either GCC or Clang
produces.
22 jobs for <span class="ref-name">arm64-msac-bool</span> in 8 minutes and 2 seconds (queued for 54 seconds)
Status Job ID Name Coverage
  Style
passed #278643
debian amd64
style-check

00:00:21

 
  Build
passed #278644
debian amd64
build-debian

00:00:38

passed #278652
debian aarch64
build-debian-aarch64

00:01:34

passed #278653
debian aarch64
build-debian-aarch64-clang-5

00:01:12

passed #278656
debian armv7
build-debian-armv7

00:01:23

passed #278657
debian armv7
build-debian-armv7-clang-5

00:01:03

passed #278645
debian amd64
build-debian-static

00:00:37

passed #278655
debian aarch64
build-debian-werror

00:00:37

passed #278646
debian amd64
build-debian32

00:00:38

passed #278654
macos
build-macos

00:00:28

passed #278658
debian amd64 allowed to fail
build-ubuntu-snap

00:00:40

passed #278650
debian amd64
build-win-arm32

00:00:29

passed #278651
debian amd64
build-win-arm64

00:00:29

passed #278647
debian amd64
build-win32

00:00:41

passed #278648
debian amd64
build-win32-unaligned-stack

00:00:40

passed #278649
debian amd64
build-win64

00:00:51

 
  Test
passed #278659
debian amd64
test-debian

00:00:48

passed #278661
debian amd64
test-debian-asan

00:02:24

passed #278662
debian amd64
test-debian-msan

00:01:09

passed #278663
debian amd64
test-debian-ubsan

00:01:32

passed #278660
debian amd64
test-debian-unaligned-stack

00:00:55

passed #278664
debian amd64
test-win64

00:00:54