google/buddy: Add board as variant of google/auron

Add google/buddy (Acer Chromeboase 24) as a variant of google/auron,
with the following changes:

- add buddy-specific variant code
- add handling to auron for buddy's lan init, which no other variants have
- add handling to auron's mainboard ACPI due buddy having different PCIe
  port assigments than all other variants

Ported from Chromium branch firmware-buddy-6301.202.B, commit
ebb82ce [Buddy: Lock management engine + SPI descriptor]

Test: build/boot Linux on google/buddy using SeaBIOS and Tianocore payloads

Change-Id: Ib76eef47677b72ddaef81a2decef189a5f20c20a
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/28613
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/google/auron/variant.h

@@ -20,5 +20,6 @@
 
 int variant_smbios_data(device_t dev, int *handle, unsigned long *current);
 void variant_romstage_entry(struct romstage_params *rp);
+void lan_init(void);
 
 #endif