spi_mpc83xx.c: support QE enabled 83xx CPU's like mpc832x

Quicc Engine enabled mpc83xx CPU's has a somewhat different HW interface to
the SPI controller.  This patch adds a qe_mode knob that sees to that
needed adaptions are performed.

Signed-off-by: Joakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>