[OpenCL] opencl-c.h: Add const to get_image_num_samples

[svenvh]

Summary

Align with the -fdeclare-opencl-builtins option and other
get_image_* builtins which have the const attribute.

[Anastasia]

LGTM! Thanks

clang/lib/Headers/opencl-c.h

 size_t __ovld __cnfn get_image_array_size(read_write image2d_array_msaa_depth_t);
 #endif //cl_khr_gl_msaa_sharing
 #endif //defined(__opencl_c_read_write_images)
 
 /**
 * Return the number of samples associated with image
 */
 #if defined(cl_khr_gl_msaa_sharing)
-int __ovld get_image_num_samples(read_only image2d_msaa_t);
-int __ovld get_image_num_samples(read_only image2d_msaa_depth_t);
-int __ovld get_image_num_samples(read_only image2d_array_msaa_t);
-int __ovld get_image_num_samples(read_only image2d_array_msaa_depth_t);
-
-int __ovld get_image_num_samples(write_only image2d_msaa_t);
-int __ovld get_image_num_samples(write_only image2d_msaa_depth_t);
-int __ovld get_image_num_samples(write_only image2d_array_msaa_t);
-int __ovld get_image_num_samples(write_only image2d_array_msaa_depth_t);
+int __ovld __cnfn get_image_num_samples(read_only image2d_msaa_t);
+int __ovld __cnfn get_image_num_samples(read_only image2d_msaa_depth_t);
+int __ovld __cnfn get_image_num_samples(read_only image2d_array_msaa_t);
+int __ovld __cnfn get_image_num_samples(read_only image2d_array_msaa_depth_t);
+
+int __ovld __cnfn get_image_num_samples(write_only image2d_msaa_t);
+int __ovld __cnfn get_image_num_samples(write_only image2d_msaa_depth_t);
+int __ovld __cnfn get_image_num_samples(write_only image2d_array_msaa_t);
+int __ovld __cnfn get_image_num_samples(write_only image2d_array_msaa_depth_t);
 
 #if defined(__opencl_c_read_write_images)
-int __ovld get_image_num_samples(read_write image2d_msaa_t);
-int __ovld get_image_num_samples(read_write image2d_msaa_depth_t);
-int __ovld get_image_num_samples(read_write image2d_array_msaa_t);
-int __ovld get_image_num_samples(read_write image2d_array_msaa_depth_t);
+int __ovld __cnfn get_image_num_samples(read_write image2d_msaa_t);
+int __ovld __cnfn get_image_num_samples(read_write image2d_msaa_depth_t);
+int __ovld __cnfn get_image_num_samples(read_write image2d_array_msaa_t);
+int __ovld __cnfn get_image_num_samples(read_write image2d_array_msaa_depth_t);
 #endif //defined(__opencl_c_read_write_images)
 #endif
 
 // OpenCL v2.0 s6.13.15 - Work-group Functions
 
 #if defined(__opencl_c_work_group_collective_functions)
 int __ovld __conv work_group_all(int predicate);
 int __ovld __conv work_group_any(int predicate);