mesa: remove the dstX/Y/Zoffset params to _mesa_texstore() functions

mesa: remove the dstX/Y/Zoffset params to _mesa_texstore() functions

The were always zero.  When doing a sub-texture replacement we account
for the dstX/Y/Zoffsets when we map the texture image.  So no need to
pass them into the texstore code anymore.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>