ARM: 6033/1: ARM: MMCI: pass max frequency from platform

This introduce the field f_max into the mmci_platform_data,
making it possible to pass in a desired block clocking frequency
from a board configuration. This is often more desirable than
using a module parameter. We keep the module parameter as a
fallback as well as the default frequency specified for this
parameter if a parameter is not provided.

This also adds some kerneldoc style documentation to the
platform data struct in mmci.h.

Signed-off-by: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>