gpiolib: acpi: Set label for IRQ only lines

When line locked as IRQ it has no label assigned. Assign
the meaningful value to it.

Ex. (for the PCA9355 and MAX3111e chips connected to the system):

=== Before ===
PCA953x:        interrupt
MAX3111e:       interrupt

=== After ===
PCA953x:        NIO1 GpioInt(0)
MAX3111e:       URT0 GpioInt(0)

Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>