drm/radeon/kms: fix bad cast/shift in evergreen.c

Missing parens.

fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=30718

Reported-by: Dave Gilbert <freedesktop@treblig.org>
Signed-off-by: Alex Deucher <alexdeucher@gmail.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Cc: stable@kernel.org
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/radeon/evergreen.c

@@ -1137,7 +1137,7 @@ static void evergreen_gpu_init(struct radeon_device *rdev)
 
 		WREG32(RCU_IND_INDEX, 0x203);
 		efuse_straps_3 = RREG32(RCU_IND_DATA);
-		efuse_box_bit_127_124 = (u8)(efuse_straps_3 & 0xF0000000) >> 28;
+		efuse_box_bit_127_124 = (u8)((efuse_straps_3 & 0xF0000000) >> 28);
 
 		switch(efuse_box_bit_127_124) {
 		case 0x0: