ARM: OMAP: Add bitbank SPI driver for Innovator 1510 touchscreen

Add bitbang SPI driver for Innovator 1510 touchscreen, using the new
framework.  Compile-tested only.

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