Update vboot submodule to upstream main

Updating from commit id 61971455:
    vboot_ref/Makefile: Expose symbols irregardless of USE_FLASHROM

to commit id a975eed3:
    2kernel.c: check display request in vb2api_kernel_phase2

This brings in 20 new commits.

BUG=b:172339016
TEST=builds with vboot_ref uprev.

Signed-off-by: Selma Bensaid <selma.bensaid@intel.com>
Change-Id: I8f9339f169c4c16216a9f380a7ca00a36098d7f8
Reviewed-on: https://review.coreboot.org/c/coreboot/+/65955
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jérémy Compostella <jeremy.compostella@intel.com>
Reviewed-by: Julius Werner <jwerner@chromium.org>

1 files changed, 0 insertions, 0 deletions

diff --git a/3rdparty/vboot b/3rdparty/vboot
-Subproject 61971455ccb99fc6da03c493dfcda102e71aee2
+Subproject a975eed306e16947c30b48ccd25ab67a3729574