tg3: Set card 57765 card reader MRRS to 1024B

This patch sets the Maximum Read Request Size for the card reader
function to 1024 bytes to prevent an SD controller lockup.

Signed-off-by: Matt Carlson <mcarlson@broadcom.com>
Reviewed-by: Michael Chan <mchan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>