drm/i915/guc/slpc: Add methods to set min/max frequency

Add param set h2g helpers to set the min and max frequencies
for use by SLPC.

v2: Address review comments (Michal W)
v3: Check for positive error code (Michal W)
v4: Print generic error in set_param (Michal W)

Reviewed-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Signed-off-by: Sundaresan Sujaritha <sujaritha.sundaresan@intel.com>
Signed-off-by: Vinay Belgaumkar <vinay.belgaumkar@intel.com>
Signed-off-by: John Harrison <John.C.Harrison@Intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210730202119.23810-8-vinay.belgaumkar@intel.com