drm/i915/gen11: Moving WAs to rcs_engine_wa_init()

This are register of render engine, so after a render reset those
would return to the default value and init_clock_gating() is not
called for single engine reset.
So here moving it rcs_engine_wa_init() that will guarantee that this
WAs will not be lost.

Cc: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200302231421.224322-1-jose.souza@intel.com