brcm63xx: initial support for Sky SR102 router

brcm63xx: initial support for Sky SR102 router

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SOC: 	    BCM63168 (BMIPS4350 V8.0 @400MHz)
Flash size: 16 MiB
RAM size:   128 MiB

Heavily based on patch for OpenWRT Chaos Chalmer.
Original patch and more info can be found at:
https://openwrt.org/toh/sky/sr102

Known issues:
 - Wireless and ADSL modem are not working.

Signed-off-by: Andrius Štikonas <andrius@stikonas.eu>