mmc: constify mmc_host_ops vectors

Now that mmc_host_ops can be constified, update the various drivers
to constify those method tables and shrink the writable data segment.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Pierre Ossman <drzeus@drzeus.cx>
diff --git a/drivers/mmc/at91_mci.c b/drivers/mmc/at91_mci.c
index 494b23f..6495cd8 100644
--- a/drivers/mmc/at91_mci.c
+++ b/drivers/mmc/at91_mci.c
@@ -793,7 +793,7 @@
 	return read_only;
 }
 
-static struct mmc_host_ops at91_mci_ops = {
+static const struct mmc_host_ops at91_mci_ops = {
 	.request	= at91_mci_request,
 	.set_ios	= at91_mci_set_ios,
 	.get_ro		= at91_mci_get_ro,