bcm27xx: add bit variant to redundant RaspberryPi

bcm27xx: add bit variant to redundant RaspberryPi

Both bcm2709 and bcm2710 firmware can run on the same RaspberryPi
models, varying however in 32 and 64 Bit architectures. The model name
alone does not include the architecture information, which becomes
problematic if looking at a overview that only contains the names. By
adding a variant it is possible to tell the architecture.

Signed-off-by: Paul Spooren <mail@aparcar.org>