If we specify an GPIO which cannot be used for the purpose, then assume
that the GPIO is not to be used and do not try and configure it.  This can
be the case where the SPI bus is TX only.
Signed-off-by: NBen Dooks <ben-linux@fluff.org>
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>