spi: bcm2835aux: spi: add bindings for the bcm2835 auxiliary spi devices

This defines the spi1 and spi2 devices in the device-tree.

Signed-off-by: Martin Sperl <kernel@martin.sperl.org>
Acked-by: Stephen Warren <swarren@wwwdotorg.org>
Signed-off-by: Mark Brown <broonie@kernel.org>