soc: qcom: ubwc: Fix missing include

When CONFIG_QCOM_UBWC_CONFIG=n, compiler needs to know the definition
of ERR_PTR otherwise there will be a compilation error:

In file included from drivers/gpu/drm/msm/disp/dpu1/dpu_hw_sspp_v13.c:7:
./include/linux/soc/qcom/ubwc.h: In function ‘qcom_ubwc_config_get_data’:
./include/linux/soc/qcom/ubwc.h:45:16: error: implicit declaration of
function ‘ERR_PTR’ [-Wimplicit-function-declaration]

Fix this by including <linux/err.h>

Fixes: 1924272b9c ("soc: qcom: Add UBWC config provider")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Reviewed-by: Konrad Dybcio <konrad.dybcio@oss.qualcomm.com>
Signed-off-by: Daniel Baluta <daniel.baluta@nxp.com>
Tested-by: Nathan Chancellor <nathan@kernel.org> # build
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

include/linux/soc/qcom/ubwc.h

@@ -8,6 +8,7 @@
 #define __QCOM_UBWC_H__
 
 #include <linux/bits.h>
+#include <linux/err.h>
 #include <linux/printk.h>
 #include <linux/types.h>