vboot_aux_fw: Add new return code to handle busy case
vboot_aux_fw: Add new return code to handle busy case

We do not want to upgrade the TCPC firmware if the TCPC is the only
source of power. Use this new return code to communicate to depthcharge
that we do not want upgrade at this time.

BRANCH=none
BUG=b:78334391
TEST=if PS8751 is the only source of power, then upgrade will gracefully
skip.

Change-Id: I062c79a2d01f779c30873d48ff4301aca071cca3
Signed-off-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1123105
Reviewed-by: Simon Glass <c00b0378376498bd9cd974c388df8854c0131d27@chromium.org>
Reviewed-by: Furquan Shaikh <6be5c96c464778f89679b1062a2e0a6af93d2aa5@chromium.org>
Reviewed-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@google.com>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot