mfd: cpcap: Fix interrupt to use level interrupt

I made a mistake assuming the device tree configuration for interrupt
triggering was somehow passed to the SPI device but it's not.

In the Motorola Linux kernel tree CPCAP PMIC is configured as a rising
edge triggered interrupt, but then then it's interrupt handler keeps
looping until the GPIO line goes down. So the CPCAP interrupt is clearly
a level interrupt and not an edge interrupt.

Earlier when I tried to configure it as level interrupt using the
device tree, I did not account that the triggering only gets passed
to the SPI core and it also needs to be specified in the CPCAP driver
when we do devm_regmap_add_irq_chip().

Fixes: 56e1d40d ("mfd: cpcap: Add minimal support")
Signed-off-by: Tony Lindgren <tony@atomide.com>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>