anv: Fix check for isl_fmt in assert

Checking isl_fmt returned value in assert seems appropriate
instead of format variable.

Fixes: f1654fa7e3 "anv/android: support creating images from external format"
Signed-off-by: Nataraj Deshpande <nataraj.deshpande@intel.com>
Reviewed-by: Tapani Pälli <tapani.palli@intel.com>
Reviewed-by: Sagar Ghuge <sagar.ghuge@intel.com>
(cherry picked from commit d6724471a5)

src/intel/vulkan/anv_image.c

@@ -821,7 +821,7 @@ resolve_ahw_image(struct anv_device *device,
                                                 vk_format,
                                                 VK_IMAGE_ASPECT_COLOR_BIT,
                                                 vk_tiling);
-   assert(format != ISL_FORMAT_UNSUPPORTED);
+   assert(isl_fmt != ISL_FORMAT_UNSUPPORTED);
 
    /* Handle RGB(X)->RGBA fallback. */
    switch (desc.format) {