firmware/dcdbas: Constify attribute_group structures

attribute_group are not supposed to change at runtime. All functions
working with attribute_group provided by <linux/sysfs.h> work with
const attribute_group. So mark the non-const structs as const.

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Douglas_Warzecha <douglas_warzecha@dell.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/20170818194947.19347-13-ard.biesheuvel@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

drivers/firmware/dcdbas.c

@@ -534,7 +534,7 @@ static struct attribute *dcdbas_dev_attrs[] = {
 	NULL
 };
 
-static struct attribute_group dcdbas_attr_group = {
+static const struct attribute_group dcdbas_attr_group = {
 	.attrs = dcdbas_dev_attrs,
 	.bin_attrs = dcdbas_bin_attrs,
 };