soc/intel/mtl/acpi: add FSPI to DSDT

Getting an error from the Kernel on Rex devices:
> ACPI Error: AE_NOT_FOUND, While resolving a named reference
> package element - \_SB_.PCI0.FSPI (20210730/dspkginit-438)

FSPI is defined in src/soc/intel/meteorlake/chipset.cb:
device pci 1f.5 alias fast_spi on end

This CL adds the corresponding FSPI device to the DSDT to prevent
the error mentioned above.
See commit feed8e4bd9 ("soc/intel/adl/acpi: add FSPI to DSDT") for
the corresponding ADL CL.

TEST=Built and tested on brya by verifying the error is gone.

Signed-off-by: Eran Mitrani <mitrani@google.com>
Change-Id: Id8d2a1b5e074f036345e028b117d420bf36a9042
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72411
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/soc/intel/meteorlake/acpi/serialio.asl

@@ -38,6 +38,12 @@ Device (I2C5)
 	Name (_DDN, "Serial IO I2C Controller 5")
 }
 
+Device (FSPI)
+{
+	Name (_ADR, 0x001f0005)
+	Name (_DDN, "Fast SPI")
+}
+
 Device (SPI0)
 {
 	Name (_ADR, 0x001e0002)