platform/x86: serial-multi-instantiate: Add IRQ_RESOURCE_OPT for IRQ missing projects

The tas2781-hda supports multi-projects. In some projects, GpioInt() was
dropped due to no IRQ connection. See the example code below:

Device (SPKR)
{
Name (_ADR, One)
Name (_HID, "TXNW2781")
Method (_CRS, 0, NotSerialized)
{
Name (RBUF, ResourceTemplate ()
{
I2cSerialBusV2 (0x0038, ...)
I2cSerialBusV2 (0x0039, ...)
// GpioInt (Edge, ...) { 0x0000 }
//"GpioInt (...) {}" was commented out due to no IRQ connection.
})
Return (RBUF)
}
}

But in smi_i2c_probe(), smi_spi_probe() (serial-multi-instantiate.c), if
looking for IRQ by smi_get_irq() fails, it will return an error, will not add
new device, and cause smi_probe() to fail:

[ 2.356546] Serial bus multi instantiate pseudo device driver TXNW2781:00:
error -ENXIO: IRQ index 0 not found
[ 2.356561] Serial bus multi instantiate pseudo device driver TXNW2781:00:
error -ENXIO: Error requesting irq at index 0

So, we need to add an exception case for these situations. BTW, this patch
will take effect on both I2C and SPI devices.

Signed-off-by: Baojun Xu <baojun.xu@ti.com>
Reviewed-by: Hans de Goede <johannes.goede@oss.qualcomm.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20251126141434.11110-1-baojun.xu@ti.com
Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>