mmc: Allow host drivers to specify a max block size

Most controllers have an upper limit on the block size. Allow the host
drivers to specify this and make sure we avoid hitting this limit.

Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
diff --git a/drivers/mmc/pxamci.c b/drivers/mmc/pxamci.c
index 6073d99..9fc9aed1 100644
--- a/drivers/mmc/pxamci.c
+++ b/drivers/mmc/pxamci.c
@@ -450,6 +450,11 @@
 	 */
 	mmc->max_seg_size = PAGE_SIZE;
 
+	/*
+	 * Block length register is 10 bits.
+	 */
+	mmc->max_blk_size = 1023;
+
 	host = mmc_priv(mmc);
 	host->mmc = mmc;
 	host->dma = -1;