When the GL_EXT_unpack_subimage extension is not available and a
subregion of a texture is uploaded then it should first copy the
subregion to a newly allocated bitmap. However it was then later still
trying to prepare the upload using the original src_x and src_y values
which would cause an assertion failure. This patch fixes it to just
reset those to zero if the subregion is first copied.
Reviewed-by: Robert Bragg <robert@linux.intel.com>
(cherry picked from commit 6f9a62db6f846f1d76e3ca16d9d8cdadf82a7009)
b3f56ccb48