ARM: bcm2835: add the auxiliary spi1 and spi2 to the device tree

This enables the use of the auxiliary spi1 and spi2 devices
on the bcm2835 SOC.

Note that this requires the use of the new clk-bcm2835-aux to work.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
[anholt: Rebased on 2835.dtsi -> 283x.dtsi change]
Signed-off-by: Eric Anholt <eric@anholt.net>