spi: Freescale STMP driver

Add SPI driver for Freescale STMP 3xxx-based boards

[dbrownell@users.sourceforge.net: cleanup sequence, spi_unregister_master]
Signed-off-by: dmitry pervushin <dpervushin@embeddedalley.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Kumar Gala <galak@gate.crashing.org>
Cc: Timur Tabi <timur@freescale.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>