mfd: cpcap: Fix interrupt regression with regmap clear_ack

With commit 3a6f0fb7b8eb ("regmap: irq: Add support to clear ack
registers"), the cpcap interrupts are no longer getting acked properly
leading to a very unresponsive device with CPUs fully loaded spinning
in the threaded IRQ handlers.

To me it looks like the clear_ack commit above actually fixed a long
standing bug in regmap_irq_thread() where we unconditionally acked the
interrupts earlier without considering ack_invert. And the issue with
cpcap started happening as we now also consider ack_invert.

Tim Harvey <[email protected]> tried to fix this issue earlier with
"[PATCH v2] regmap: irq: fix ack-invert", but the reading of the ack
register was considered unnecessary for just ack_invert, and we did not
have clear_ack available yet. As the cpcap irqs worked both with and
without ack_invert earlier because of the unconditional ack, the
problem remained hidden until now.

Also, looks like the earlier v3.0.8 based Motorola Android Linux kernel
does clear_ack style read-clear-write with "ireg_val & ~mreg_val" instead
of just ack_invert style write. So let's switch cpcap to use clear_ack
to fix the issue.

Fixes: 3a6f0fb7b8eb ("regmap: irq: Add support to clear ack registers")
Cc: Carl Philipp Klemm <[email protected]>
Cc: Laxminath Kasam <[email protected]>
Cc: Merlijn Wajer <[email protected]>
Cc: Mark Brown <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Sebastian Reichel <[email protected]>
Cc: Tim Harvey <[email protected]>
Signed-off-by: Tony Lindgren <[email protected]>
Tested-by: Pavel Machek <[email protected]>
Reviewed-By: Tim Harvey <[email protected]>
Signed-off-by: Lee Jones <[email protected]>

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