spi: pxa2xx_spi "sparse" fixes

Various cleanups to pxa2xx_spi suggested by "sparse": make sure that
register addresess are "void __iomem *", and make a few functions properly
static.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Ned Forrester <nforrester@whoi.edu>
Cc: Stephen Street <stephen@streetfiresound.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>