Staging: android: ion: Make a read-only structure

This patch add const qualifier at the declaration of the structure.
The structure become a read-only data, this increase the security.

Found with Coccinelle:
@r disable optional_qualifier@
identifier s,i;
@@
* static struct s i ={...};
Signed-off-by: Mihaela Muraru <mihaela.muraru21@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/android/ion/ion_dummy_driver.c

@@ -58,7 +58,7 @@ static struct ion_platform_heap dummy_heaps[] = {
 		},
 };
 
-static struct ion_platform_data dummy_ion_pdata = {
+static const struct ion_platform_data dummy_ion_pdata = {
 	.nr = ARRAY_SIZE(dummy_heaps),
 	.heaps = dummy_heaps,
 };