firmware: bcm2835: Support ARCH_BCM270x

Support booting without Device Tree.
Turn on USB power.
Load driver early because of lacking support for deferred probing
in many drivers.

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>

firmware: bcm2835: Don't turn on USB power

The raspberrypi-power driver is now used to turn on USB power.

This partly reverts commit:
firmware: bcm2835: Support ARCH_BCM270x

Signed-off-by: Noralf Trønnes <noralf@tronnes.org>