mfd: Prevent STMPE from abusing mfd_add_devices' irq_base parameter

Originally IRQ incrementers were provided in some template resource
structures for keypad and touchscreen devices. These were passed as
IORESOURCE_IRQs to MFD core in the usual way. The true device IRQs
were instead added to the irq_base when mfd_add_devices was invoked.
This is clearly an abuse of the call, and does not scale when IRQ
Domains are brought into play. Before we can provide the STMPE with
its own IRQ Domain we must first fix this. This patche keeps most
of the driver's structure, keeping the template strategy. However,
instead of providing the IRQ as an increment to irq_base, we
dynamically populate the IORESOURCE_IRQ with the correct device IRQ.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>