mesa: Silence unused parameter warning in compressedteximage_only_format

mesa: Silence unused parameter warning in compressedteximage_only_format

Passing ctx to compressedteximage_only_format was the only use of the
ctx parameter in _mesa_format_no_online_compression, so that parameter
had to go too.

../../SOURCE/master/src/mesa/main/teximage.c: In function ‘compressedteximage_only_format’:
../../SOURCE/master/src/mesa/main/teximage.c:1355:57: warning: unused parameter ‘ctx’ [-Wunused-parameter]
 compressedteximage_only_format(const struct gl_context *ctx, GLenum format)
                                                         ^~~

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Brian Paul <brianp@vmware.com>