pinctrl: qcom: spmi-gpio: correct parent irqspec translation

pmic_gpio_child_to_parent_hwirq() and
gpiochip_populate_parent_fwspec_fourcell() translate a pinctrl-
spmi-gpio irqspec to an SPMI controller irqspec.  When they do
this, they use a fixed SPMI slave ID of 0 and a fixed GPIO
peripheral offset of 0xC0 (corresponding to SPMI address 0xC000).
This translation results in an incorrect irqspec for secondary
PMICs that don't have a slave ID of 0 as well as for PMIC chips
which have GPIO peripherals located at a base address other than
0xC000.

Correct this issue by passing the slave ID of the pinctrl-spmi-
gpio device's parent in the SPMI controller irqspec and by
calculating the peripheral ID base from the device tree 'reg'
property of the pinctrl-spmi-gpio device.

Change-Id: If04a7ca73b995dd99939d340f2d33d4488197de0
Signed-off-by: David Collins <collinsd@codeaurora.org>