[PATCH] minor SPI doc fix

Because several developers asked me about referenced but missing
spi_add_master(), I think that this patch should be applied ...  it
corrects comments so they refer to spi_register_master() instead.

Signed-off-by: dmitry pervushin <dpervushin@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>