drm/i915/guc/slpc: Correct the param count for unset param

SLPC unset param H2G only needs one parameter - the id of the
param.

Fixes: 025cb07bebfa ("drm/i915/guc/slpc: Cache platform frequency limits")

Suggested-by: Umesh Nerlige Ramappa <[e-mail]>
Signed-off-by: Vinay Belgaumkar <[e-mail]>
Reviewed-by: Umesh Nerlige Ramappa <[e-mail]>
Signed-off-by: Ramalingam C <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]
(cherry picked from commit 9648f1c3739505557d94ff749a4f32192ea81fe3)
Signed-off-by: Tvrtko Ursulin <[e-mail]>

drivers/gpu/drm/i915/gt/uc/intel_guc_slpc.c

···
 {
 	u32 request[] = {
 		GUC_ACTION_HOST2GUC_PC_SLPC_REQUEST,
-		SLPC_EVENT(SLPC_EVENT_PARAMETER_UNSET, 2),
+		SLPC_EVENT(SLPC_EVENT_PARAMETER_UNSET, 1),
 		id,
 	};