tools/squashfs4: bump to 4.6.1

tools/squashfs4: bump to 4.6.1

Changelogs:
https://github.com/plougher/squashfs-tools/blob/4.6.1/CHANGES

Removed upstreamed patches:
- 001-Unsquashfs-Add-and-make-some-header-includes-conditi.patch
- 002-Mksquashfs-Make-sysinfo-conditional.patch
- 003-Only-use-available-CPUs.patch
- 004-action-rework-strdupa-with-POSIX-strdup-and-free.patch
- 005-Don-t-use-sigwaitinfo-sigtimedwait-if-not-supported.patch
- 006-Move-sysinfo.h-into-the-linux-only-section-should-fi.patch
- 007-Unsquashfs-fix-compilation-error-for-missing-sysctl..patch
- 100-portability.patch

Signed-off-by: Linhui Liu <liulinhui36@gmail.com>