mmc: at91_mci: enable large data blocks

This patch is setting some max_ variables for the IO elevator, so the
elevator will put requests for large data blocks to the driver.  This is
critical for

a) speed

and

b) wear leveling of the flash chip controller: Otherwise the controller
   will treat the SD card badly with millions of single 4 KByte write
   commands.  This will lead to a shorter life time for the SD cards.

Signed-off-by: Wolfgang Muees <wolfgang.mues@auerswald.de>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Andrew Victor <avictor.za@gmail.com>
Cc: <linux-mmc@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>