vboot: remove VBOOT_SAVE_RECOVERY_REASON_ON_REBOOT option

With CL:1940398, this option is no longer needed.  Recovery
requests are not cleared until kernel verification stage is
reached.  If the FSP triggers any reboots, recovery requests
will be preserved.  In particular:

- Manual requests will be preserved via recovery switch state,
  whose behaviour is modified in CB:38779.
- Other recovery requests will remain in nvdata across reboot.

These functions now only work after verstage has run:
  int vboot_check_recovery_request(void)
  int vboot_recovery_mode_enabled(void)
  int vboot_developer_mode_enabled(void)

BUG=b:124141368, b:35576380
TEST=make clean && make test-abuild
BRANCH=none

Change-Id: I52d17a3c6730be5c04c3c0ae020368d11db6ca3c
Signed-off-by: Joel Kitching <kitching@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/38780
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/security/vboot/misc.h

@@ -49,11 +49,6 @@ static inline bool vboot_is_gbb_flag_set(enum vb2_gbb_flag flag)
  */
 int vboot_locate_firmware(struct vb2_context *ctx, struct region_device *fw);
 
-/*
- * Source: security/vboot/bootmode.c
- */
-void vboot_save_recovery_reason_vbnv(void);
-
 /*
  * The stage loading code is compiled and entered from multiple stages. The
  * helper functions below attempt to provide more clarity on when certain