[ARM] 4709/1: pxa: mmc: add 26MHz support for pxa3[0|1]0 mmc controller

pxa3[0|1]0 mmc controller can support 26MHz clock mode, they support
SD spec 1.1 and MMC spec 4.0 which specify high speed mode. So host
caps will include MMC_CAP_MMC_HIGHSPEED and MMC_CAP_SD_HIGHSPEED for
pxa3[0|1]0.

This patch is to add 26MHz support for them. pxa host clock will be
set to 26MHz mode when the card supported max clock rate is higher
than or equal to 26MHz.

Signed-off-by: Bridge Wu <bridge.wu@marvell.com>
Acked-by: Pierre Ossman <drzeus@drzeus.cx>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>