brcm63xx: improve BCM6318 support

brcm63xx: improve BCM6318 support

Provide clock toggling for the USB host and slave controller as well as
for the Ethernet Switch. The bcm63xx_enetsw driver is changed not to use
request_mem_region() as the Roboswitch register overlaps with the
Roboswitch IUDMA channels, hence making the driver return -EBUSY. A
future fix might be to use variable size RSET_ENETSW sizes depending on
the chip we are targetting.

Signed-off-by: Florian Fainelli <florian@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@39282 3c298f89-4303-0410-b956-a3cf2f4a3e73