Initial BF54x SPI support

 - support BF54x SPI0
 - clean up some code (whitespace etc)
 - will support multiports in the future
 - start using portmux calls
Signed-off-by: NBryan Wu <bryan.wu@analog.com>
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>