mesa: Don't check for image->Data when freeing an image's contents.

mesa: Don't check for image->Data when freeing an image's contents.

All driver implementations of FreeTextureImageBuffer already check
that Data != NULL and free it.  However, this means that we will also
free driver storage if the driver storage wasn't in the form of a Data
pointer.

This was produced by the following semantic patch:

@@
expression C;
expression T;
@@
- if (T->Data) {
- C->Driver.FreeTextureImageBuffer(C, T);
+ C->Driver.FreeTextureImageBuffer(C, T);
- }

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>