drm/xe/uapi: Remove MMIO ioctl

This was previously used in UMD for timestamp correlation, which can now
be done with DRM_XE_QUERY_CS_CYCLES.

Link: https://lore.kernel.org/all/20230706042044.GR6953@mdroper-desk1.amr.corp.intel.com/
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/636


Signed-off-by: Francois Dugast <francois.dugast@intel.com>
Reviewed-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>