drm/xe: Kill regs/xe_sriov_regs.h

There is no real benefit to maintain a separate file. The register
definitions related to SR-IOV can be placed in existing headers.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Himal Prasad Ghimiray <himal.prasad.ghimiray@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240702183704.1022-3-michal.wajdeczko@intel.com