cpufreq: powernow-k8: Mark 'hi' and 'lo' dummy variables as __always_unused

if we fail to use a variable, even a dummy ones, then the compiler
complains that it is set but not used.  We know this is fine, so we
set them as __always_unused here to let the compiler know.

Fixes the following W=1 kernel build warning(s):

 drivers/cpufreq/powernow-k8.c: In function ‘pending_bit_stuck’:
 drivers/cpufreq/powernow-k8.c:89:10: warning: variable ‘hi’ set but not used [-Wunused-but-set-variable]
 89 | u32 lo, hi;
 | ^~
 drivers/cpufreq/powernow-k8.c: In function ‘core_voltage_pre_transition’:
 drivers/cpufreq/powernow-k8.c:285:14: warning: variable ‘lo’ set but not used [-Wunused-but-set-variable]
 285 | u32 maxvid, lo, rvomult = 1;
 | ^~

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/powernow-k8.c

@@ -86,7 +86,7 @@ static u32 convert_fid_to_vco_fid(u32 fid)
  */
 static int pending_bit_stuck(void)
 {
-	u32 lo, hi;
+	u32 lo, hi __always_unused;
 
 	rdmsr(MSR_FIDVID_STATUS, lo, hi);
 	return lo & MSR_S_LO_CHANGE_PENDING ? 1 : 0;
@@ -282,7 +282,7 @@ static int core_voltage_pre_transition(struct powernow_k8_data *data,
 {
 	u32 rvosteps = data->rvo;
 	u32 savefid = data->currfid;
-	u32 maxvid, lo, rvomult = 1;
+	u32 maxvid, lo __always_unused, rvomult = 1;
 
 	pr_debug("ph1 (cpu%d): start, currfid 0x%x, currvid 0x%x, reqvid 0x%x, rvo 0x%x\n",
 		smp_processor_id(),