drm/amd/display/dc/dce/dce_panel_cntl: Remove unused variables 'bl_pwm_cntl' and 'pwm_period_cntl'

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

 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_panel_cntl.c: In function ‘dce_get_16_bit_backlight_from_pwm’:
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_panel_cntl.c:54:11: warning: variable ‘bl_pwm_cntl’ set but not used [-Wunused-but-set-variable]
 drivers/gpu/drm/amd/amdgpu/../display/dc/dce/dce_panel_cntl.c:53:11: warning: variable ‘pwm_period_cntl’ set but not used [-Wunused-but-set-variable]

Cc: Harry Wentland <harry.wentland@amd.com>
Cc: Leo Li <sunpeng.li@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: "Christian König" <christian.koenig@amd.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Anthony Koo <Anthony.Koo@amd.com>
Cc: amd-gfx@lists.freedesktop.org
Cc: dri-devel@lists.freedesktop.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/dce/dce_panel_cntl.c

@@ -50,16 +50,16 @@ static unsigned int dce_get_16_bit_backlight_from_pwm(struct panel_cntl *panel_c
 {
 	uint64_t current_backlight;
 	uint32_t round_result;
-	uint32_t pwm_period_cntl, bl_period, bl_int_count;
-	uint32_t bl_pwm_cntl, bl_pwm, fractional_duty_cycle_en;
+	uint32_t bl_period, bl_int_count;
+	uint32_t bl_pwm, fractional_duty_cycle_en;
 	uint32_t bl_period_mask, bl_pwm_mask;
 	struct dce_panel_cntl *dce_panel_cntl = TO_DCE_PANEL_CNTL(panel_cntl);
 
-	pwm_period_cntl = REG_READ(BL_PWM_PERIOD_CNTL);
+	REG_READ(BL_PWM_PERIOD_CNTL);
 	REG_GET(BL_PWM_PERIOD_CNTL, BL_PWM_PERIOD, &bl_period);
 	REG_GET(BL_PWM_PERIOD_CNTL, BL_PWM_PERIOD_BITCNT, &bl_int_count);
 
-	bl_pwm_cntl = REG_READ(BL_PWM_CNTL);
+	REG_READ(BL_PWM_CNTL);
 	REG_GET(BL_PWM_CNTL, BL_ACTIVE_INT_FRAC_CNT, (uint32_t *)(&bl_pwm));
 	REG_GET(BL_PWM_CNTL, BL_PWM_FRACTIONAL_EN, &fractional_duty_cycle_en);