spmi: pmic_arb: add support for interrupt handling

The Qualcomm PMIC Arbiter, in addition to being a basic SPMI controller,
also implements interrupt handling for slave devices.  Note, this is
outside the scope of SPMI, as SPMI leaves interrupt handling completely
unspecified.

Extend the driver to provide a irq_chip implementation and chained irq
handling which allows for these interrupts to be used.

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Josh Cartwright <joshc@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/spmi/Kconfig

@@ -13,6 +13,7 @@ if SPMI
 config SPMI_MSM_PMIC_ARB
 	tristate "Qualcomm MSM SPMI Controller (PMIC Arbiter)"
 	depends on ARM
+	depends on IRQ_DOMAIN
 	depends on ARCH_MSM || COMPILE_TEST
 	default ARCH_MSM
 	help