vboot: adjust VB2_SECDATA_KERNEL_FLAGS in non-recovery path

Currently, VB2_SECDATA_KERNEL_FLAGS controls experimental features
like phone recovery (and its UI), diagnostics entry. All of those
are under recovery screen. In order to allow later update pushes to
enable specific features in write-protected RO, we should not set
those flags in recovery path. Otherwise, it will always toggle back
and forth when booting RO recovery path vs. normal boot path.

TEST=MENU_UI=0 DIAGNOSTIC_UI=0 make runtests
TEST=MENU_UI=0 DIAGNOSTIC_UI=1 make runtests
TEST=MENU_UI=1 DIAGNOSTIC_UI=0 make runtests
TEST=MENU_UI=1 DIAGNOSTIC_UI=1 make runtests
TEST=Cherry-pick locally to ToT of firmware-puff-13324.B with
     chromium:2360066 to manually check flags on Kaisa device.

Change-Id: I7ec45b4ecfa6d50781cec2690dbc88894c734073
Signed-off-by: Chun-Ta Lin <itspeter@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/2361983
Tested-by: Chun-ta Lin <itspeter@chromium.org>
Reviewed-by: Joel Kitching <kitching@chromium.org>
Commit-Queue: Chun-ta Lin <itspeter@chromium.org>
2 files changed