[S] Change in coreboot[master]: security/vboot: Add function to clear recovery request

[Yu-Ping Wu (Code Review)]

Attention is currently required from: Michał Żygowski.

Yu-Ping Wu has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/74343 )

Change subject: security/vboot: Add function to clear recovery request
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Patch Set 3:

(1 comment)

File src/security/vboot/bootmode.c:

https://review.coreboot.org/c/coreboot/+/74343/comment/3682bc7d_e600444e 
PS3, Line 31: save_vbnv
Do we need to save nvdata here in this function? Usually it should be sufficient to save nvdata right before rebooting (for example `vboot_save_and_reboot`), or before handoff to the next boot stage (for ChromeOS we do this in depthcharge before handoff to kernel), instead of having to save it for each nvdata change.

I wonder if we can extend `BOOT_STATE_INIT_ENTRY(BS_POST_DEVICE, BS_ON_EXIT, back_up_vbnv_cmos)` to also saving nvdata, when some Kconfig option `VBOOT_SAVE_VBNV_BEFORE_PAYLOAD` is enabled (and only when `VB2_CONTEXT_NVDATA_CHANGED`).