Blackfin SPI Driver: use bfin_spi_ prefix on all functions

Do this because when things crash, we get simple names like "setup" and
"start_queue" which is pretty difficult to trace back to the real thing:
the spi driver

Signed-off-by: Mike Frysinger <vapier.adi@gmail.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>