[S] Change in coreboot[main]: payloads/ipxe/makefile: Use git reset for resetting config state

[Nico Huber (Code Review)]

Attention is currently required from: Felix Singer, Filip Lewiński, Maciej Pijanowski, Martin L Roth, Michał Żygowski, Nicholas Chin.

Nico Huber has posted comments on this change by Felix Singer. ( https://review.coreboot.org/c/coreboot/+/83363?usp=email )

Change subject: payloads/ipxe/makefile: Use git reset for resetting config state
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Patch Set 4:

(2 comments)

File payloads/external/iPXE/Makefile:

https://review.coreboot.org/c/coreboot/+/83363/comment/c6f079f3_e0ff14ea?usp... :
PS4, Line 35: config: checkout
`checkout` might already fail due to the dirty tree. So maybe move the cleanup there?

https://review.coreboot.org/c/coreboot/+/83363/comment/eb0a0182_d1c0f21c?usp... :
PS4, Line 37: 		git reset --hard
Why not
```
git -C $(project_dir) checkout -- src/config/console.h src/config/serial.h src/config/general.h
```
This would not undo unrelated changes, e.g. if somebody tries some code change.