drm/xe: Use function to emit PIPE_CONTROL

This reduces code duplication in xe_ring_ops.

v2:
- fix flags of emit_pipe_imm_ggtt()
- reduce to only one function

v3:
- fix emit_pipe_imm_ggtt() stall_only check

Cc: Matt Roper <matthew.d.roper@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240130132249.8615-1-jose.souza@intel.com