Change in coreboot[master]: mb/google/volteer/variants/drobit: Add TBT PCIE rp setting for drobit

[Zhuohao Lee (Code Review)]

Attention is currently required from: Wayne3 Wang, Hank Lin, Tim Wawrzynczak, Nick Vaccaro, Ken Lu, Zhuohao Lee.
Zhuohao Lee has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50103 )

Change subject: mb/google/volteer/variants/drobit: Add TBT PCIE rp setting for drobit
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Patch Set 1:

(1 comment)

File src/mainboard/google/volteer/variants/drobit/overridetree.cb:

https://review.coreboot.org/c/coreboot/+/50103/comment/3543eef9_3f7d6c54 
PS1, Line 63: 		device ref tbt_pcie_rp0 on end
            : 		device ref tbt_pcie_rp1 on end
> I try to add the "probe DB_USB USB4_GEN3" to tbt_pcie_rp0 and tbt_pcie_rp1. […]

Do you check the FW_CONFIG in the CBI? The bit 0-3 should be set to 0011b. Please refer to baseboard/devicetree.cb