gpio: uniphier: Fix void functions to remove return value

gpio: uniphier: Fix void functions to remove return value

BugLink: https://bugs.launchpad.net/bugs/1949640
[ Upstream commit 2dd824cca3407bc9a2bd11b00f6e117b66fcfcf1 ]

The return type of irq_chip.irq_mask() and irq_chip.irq_unmask() should
be void.

Fixes: dbe776c2ca54 ("gpio: uniphier: add UniPhier GPIO controller driver")
Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko@socionext.com>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>