Change in coreboot[master]: mb/google/brya/var/primus{4es}: add enable pin to rtd3-cold

[Tim Wawrzynczak (Code Review)]

Attention is currently required from: Casper Chang.
Tim Wawrzynczak has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/62586 )

Change subject: mb/google/brya/var/primus{4es}: add enable pin to rtd3-cold
......................................................................

Patch Set 2: Code-Review+2

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/62586/comment/57b4b5ce_0de52704 
PS2, Line 9: add enable pin to rtd3-cold for primus{4es}.
suggestion:
```
Currently the BayHub eMMC controller is only going into its reset
state when the RTD3 sequence is initiated. This causes it to 
still consume too much power in suspend states. This CL adds the
power enable GPIO into the RTD3 sequence as well, which will turn
off the eMMC controller (a true D3cold state) during the RTD3
sequence.
```