drm/imx: imx-ldb: Check for null pointer after calling kmemdup

drm/imx: imx-ldb: Check for null pointer after calling kmemdup

[ Upstream commit 8190101133554395eec3f17ed89e827211c999f9 ]

As the possible failure of the allocation, kmemdup() may return NULL
pointer.
Therefore, it should be better to check the return value of kmemdup()
and return error if fails.

Fixes: 541ac3bcf9a3 ("drm/imx-ldb: Add support to drm-bridge")
Signed-off-by: Jiasheng Jiang <jiasheng@iscas.ac.cn>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Link: https://lore.kernel.org/r/20220105074729.2363657-1-jiasheng@iscas.ac.cn
Signed-off-by: Sasha Levin <sashal@kernel.org>