kernel: bump 4.9 to 4.9.54
Refresh patches.
Remove upstreamed patches:
- ramips/0067-enable-mt7621-xhci.patch
- ramips/0085-pinmux-util.patch
- ramips/301-fix-rt3883.patch
Compile-tested on brcm2708/bcm2708, octeon, ramips/mt7621, x86/64.
Runtime-tested on brcm2708/bcm2708, octeon, ramips/mt7621, x86/64.
Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be>