regmap-irq: Fix offset/index mismatch in read_sub_irq_data()

[ Upstream commit 3f05010f ]

We need to divide the sub-irq status register offset by register
stride to get an index for the status buffer to avoid an out of
bounds write when the register stride is greater than 1.

Fixes: a2d21848 ("regmap: regmap-irq: Add main status register support")
Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
Link: https://lore.kernel.org/r/20220620200644.1961936-3-aidanmacdonald.0x0@gmail.com


Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>