SPI: omap2_mcspi driver

Add OMAP24XX McSPI (Multichannel SPI) controller driver.  This driver is
tested very well under OMAP GIT tree with N800 - Nokia Internet Tablet, and
some other OMAP2 boards.

Recent updates included bugfixes, cleanups, speedups, and better
conformance to the current SPI programming interface.  This doesn't yet
understand the third controller instance on the OMAP 2430.

[david-b@pacbell.net: more minor cleanups to the omap2_mcspi driver]
Signed-off-by: Juha Yrjölä <juha.yrjola@solidboot.com>
Signed-off-by: Trilok Soni <soni.trilok@gmail.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>