drm/radeon/evergreen: Remove set but unused variable 'mc_shared_chmap'

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

 drivers/gpu/drm/radeon/evergreen.c: In function ‘evergreen_gpu_init’:
 drivers/gpu/drm/radeon/evergreen.c:3135:6: warning: variable ‘mc_shared_chmap’ set but not used [-Wunused-but-set-variable]

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: 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/radeon/evergreen.c

@@ -3133,7 +3133,7 @@ static int evergreen_cp_resume(struct radeon_device *rdev)
 static void evergreen_gpu_init(struct radeon_device *rdev)
 {
 	u32 gb_addr_config;
-	u32 mc_shared_chmap, mc_arb_ramcfg;
+	u32 mc_arb_ramcfg;
 	u32 sx_debug_1;
 	u32 smx_dc_ctl0;
 	u32 sq_config;
@@ -3397,7 +3397,7 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
 
 	evergreen_fix_pci_max_read_req_size(rdev);
 
-	mc_shared_chmap = RREG32(MC_SHARED_CHMAP);
+	RREG32(MC_SHARED_CHMAP);
 	if ((rdev->family == CHIP_PALM) ||
 	    (rdev->family == CHIP_SUMO) ||
 	    (rdev->family == CHIP_SUMO2))