mmc: mmci: Add ARM variant with extended FIFO

New IO FPGA implementation for Versatile Express boards contain
MMCI (PL180) cell with FIFO extended to 128 words (512 bytes).

Matt Waddel reports that this patch improves MMC performance on
his vexpress system, and also fixes "mmcblk0: error -5 transferring
data" errors.

Signed-off-by: Pawel Moll <pawel.moll@arm.com>
Tested-by: Matt Waddel <matt.waddel@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>