implement LoSSI/9-bit mode in spi-bcm2835

[msperl]

implement LoSSI/9-bit mode in spi-bcm2835 (its basic form implemented in spi-bcm2708) so that it may become a viable option for the foundation kernel.

[msperl]

note that the implementation of the spi-bcm2708 (done by @notro) is not really complete with regards to the read side of things.
This to such an extend that not even notro is using this option in the fbtft drivers he is maintaining

[msperl]

there is this commit: ab3f074, but with the above limitations...

[msperl]

it is untested, as I have no Idea what device could get used to test (and I do not own any).
Again: the "read" code is not implemented in a correct manner...

[msperl]

@notro: Any recommendation for devices with which to test this?

[notro]

Just loopback it and send 0x04 which should trigger a 24-bit read, and 0x09 which should trigger a 32-bit read. I have never actually tested LoSSI reading.
Ref. page 151, BCM2835 ARM Peripherals