crypto: omap-sham - Constify static attribute_group

The only usage of omap_sham_attr_group is to pass its address to
sysfs_{create,remove}_group(), which takes pointers to const struct
attribute_group. Make it const to allow the compiler to put it in
read-only memory.
Signed-off-by: Rikard Falkeborn <rikard.falkeborn@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/omap-sham.c

@@ -2045,7 +2045,7 @@ static struct attribute *omap_sham_attrs[] = {
 	NULL,
 };
 
-static struct attribute_group omap_sham_attr_group = {
+static const struct attribute_group omap_sham_attr_group = {
 	.attrs = omap_sham_attrs,
 };