gpio: xgene-sb: set valid IRQ type in to_irq()

xgene-sb is setup to be a hierarchical IRQ chip with the GIC as the
parent chip. xgene_gpio_sb_to_irq() currently sets the default IRQ type
to IRQ_TYPE_NONE, which the GIC loudly complains about with a WARN_ON().
Let's set the initial default to a sane value (IRQ_TYPE_EDGE_RISING)
that was determined by decoding the ACPI tables on affected hardware:

    Device (_SB.GPSB)
    {
        Name (_HID, "APMC0D15")  // _HID: Hardware ID
        Name (_CID, "APMC0D15")  // _CID: Compatible ID
        Name (_UID, "GPIOSB")  // _UID: Unique ID
        ...
        Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
        {
            ...
            Interrupt (ResourceConsumer, Edge, ActiveHigh, Exclusive, ,, )
            {
                0x00000048,
            }
            ...
        }
    }

This can be overridden later as needed with irq_set_irq_type().

Signed-off-by: Brian Masney <bmasney@redhat.com>
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>