gpio: gpio-vf610: do not touch other bits when set the target bit

[ Upstream commit 9bf3ac466faa83d51a8fe9212131701e58fdef74 ]

For gpio controller contain register PDDR, when set one target bit,
current logic will clear all other bits, this is wrong. Use operator
'|=' to fix it.

Fixes: 659d8a62 ("gpio: vf610: add imx7ulp support")
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Haibo Chen <haibo.chen@nxp.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Sasha Levin <sashal@kernel.org>