Soon there will be more flags introduced in subsequent patches, so
let's turn qe_mode into flags.

Also introduce mpc8xxx_spi_strmode() and print current SPI mode.
Signed-off-by: NAnton Vorontsov <avorontsov@ru.mvista.com>
Acked-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NKumar Gala <galak@kernel.crashing.org>