[ Upstream commit 5674a92c ]

We forgot to set "err" on this error path.

Fixes: 1a2d397a ("gpio/powerpc: Eliminate duplication of of_get_named_gpio_flags()")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>