drm/i915/perf: make oa format tables const

No reason not to be const.
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180613114929.14541-1-jani.nikula@intel.com

drivers/gpu/drm/i915/i915_perf.c

@@ -315,7 +315,7 @@ static u32 i915_oa_max_sample_rate = 100000;
  * code assumes all reports have a power-of-two size and ~(size - 1) can
  * be used as a mask to align the OA tail pointer.
  */
-static struct i915_oa_format hsw_oa_formats[I915_OA_FORMAT_MAX] = {
+static const struct i915_oa_format hsw_oa_formats[I915_OA_FORMAT_MAX] = {
 	[I915_OA_FORMAT_A13]	    = { 0, 64 },
 	[I915_OA_FORMAT_A29]	    = { 1, 128 },
 	[I915_OA_FORMAT_A13_B8_C8]  = { 2, 128 },
@@ -326,7 +326,7 @@ static struct i915_oa_format hsw_oa_formats[I915_OA_FORMAT_MAX] = {
 	[I915_OA_FORMAT_C4_B8]	    = { 7, 64 },
 };
 
-static struct i915_oa_format gen8_plus_oa_formats[I915_OA_FORMAT_MAX] = {
+static const struct i915_oa_format gen8_plus_oa_formats[I915_OA_FORMAT_MAX] = {
 	[I915_OA_FORMAT_A12]		    = { 0, 64 },
 	[I915_OA_FORMAT_A12_B8_C8]	    = { 2, 128 },
 	[I915_OA_FORMAT_A32u40_A4u32_B8_C8] = { 5, 256 },