pinctrl: qcom: pmic-gpio/mpp: of_irq_count() == npins

The number of interrupts is always equal to the number of pins
provided by the PMIC gpio and MPP hardware blocks. Count the
number of irqs to figure out the number of pins instead of adding
more compatible strings or doing math on the reg property. This
should make the code more generic and ease the number of changes
we have to make to the driver for each new pmic revision.

Cc: Ivan T. Ivanov <iivanov@mm-sol.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Reviewed-by: Andy Gross <agross@codeaurora.org>
Reviewed-by: Björn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>