power: reset: at91-reset: check properly the return value of devm_of_iomap

power: reset: at91-reset: check properly the return value of devm_of_iomap

[ Upstream commit f558c8072c3461b65c12c0068b108f78cebc8246 ]

devm_of_iomap() returns error code or valid pointer. Check its return
value with IS_ERR().

Fixes: bd3127733f2c ("power: reset: at91-reset: use devm_of_iomap")
Reported-by: Cristian Birsan <cristian.birsan@microchip.com>
Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>