[MMC] PXA: reduce the number of lines PXAMCI debug uses

There's no reason for the PXAMCI debug code to print so many lines - it
causes the kernel buffer to overflow when trying to debug this driver.
Remove some debug messages which are duplicated by core code, and
combine other messages, resulting in fewer characters written to the
kernel log.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>