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/imxmmc.c b/drivers/mmc/imxmmc.c
index bfb9ff6..2107f8a 100644
--- a/drivers/mmc/imxmmc.c
+++ b/drivers/mmc/imxmmc.c
@@ -960,6 +960,7 @@
 	mmc->max_phys_segs = 64;
 	mmc->max_sectors = 64;		/* default 1 << (PAGE_CACHE_SHIFT - 9) */
 	mmc->max_seg_size = 64*512;	/* default PAGE_CACHE_SIZE */
+	mmc->max_blk_size = 2048;
 
 	host = mmc_priv(mmc);
 	host->mmc = mmc;