drm/i915: Silence compiler warning for hsw_power_well_enable()

Not all compilers are able to determine that pg is guarded by wait_fuses
and so may think that pg is used uninitialized.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Fixes: b2891eb2531e ("drm/i915/hsw+: Add has_fuses power well attribute")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Imre Deak <imre.deak@intel.com>
Cc: Arkadiusz Hiler <arkadiusz.hiler@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171002100416.25865-1-chris@chris-wilson.co.uk
Reviewed-by: Imre Deak <imre.deak@intel.com>

drivers/gpu/drm/i915/intel_runtime_pm.c

@@ -368,7 +368,7 @@ static void hsw_power_well_enable(struct drm_i915_private *dev_priv,
 {
 	enum i915_power_well_id id = power_well->id;
 	bool wait_fuses = power_well->hsw.has_fuses;
-	enum skl_power_gate pg;
+	enum skl_power_gate uninitialized_var(pg);
 	u32 val;
 
 	if (wait_fuses) {