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

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: 26c600a1a152 ("drm/i915/guc/slpc: Cache platform frequency limits")
Suggested-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Reviewed-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@intel.com>
Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220216181504.7155-1-vinay.belgaumkar@intel.com