platform/x86: samsung-laptop: constify attribute_group structures.

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

File size before:
   text	   data	    bss	    dec	    hex	filename
   8710	   5452	     23	  14185	   3769	drivers/platform/x86/samsung-laptop.o

File size After adding 'const':
   text	   data	    bss	    dec	    hex	filename
   8774	   5388	     23	  14185	   3769	drivers/platform/x86/samsung-laptop.o

Signed-off-by: Arvind Yadav <arvind.yadav.cs@gmail.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>

drivers/platform/x86/samsung-laptop.c

@@ -1232,7 +1232,7 @@ static umode_t samsung_sysfs_is_visible(struct kobject *kobj,
 	return ok ? attr->mode : 0;
 }
 
-static struct attribute_group platform_attribute_group = {
+static const struct attribute_group platform_attribute_group = {
 	.is_visible = samsung_sysfs_is_visible,
 	.attrs = platform_attributes
 };