omap2_mcspi fixes + cleanups

Initial updates for McSPI driver:

 - bug fixes:
    * handle byte-wide tx pio correctly for multiple bytes
    * cleanup workqueue on module exit
    * allow modular build (and rmmod)
    * request_mem_region
    * remove wrongly exported driver symbol

 - cleanup:
    * remove needless debug strings from object file
    * remove needless init and exit sections from object file
    * remove superfluous get/put of spi_master
    * fix whitespace and indentation bugs
    * fix line-too-long bugs
    * use spi_master_*() calls not class_*() calls
    * use dev_*() messaging not printk

Combined with the next patch, this gives around a 10% shrink to the driver
footprint, improves correctness, and helps it get ready to merge upstream.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>