omap2_nand updates

omap2_nand updates

Minor updates to the OMAP{2,3} NAND driver:

 - Rename those buffer PIO routines as *_buf16()
 - Get rid of pointless LE16 data conversions; OMAP is always LE
 - Speed up buffer reads by switching to __raw_readsl()

Right now this driver only handles 16-bit NAND, but eventually it
should handle 8-bit too.  Moreover it may be worth using DMA...

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Tony Lindgren <tony@atomide.com>