vboot_logic: Set VB2_CONTEXT_EC_TRUSTED in verstage_main

vboot_reference is introducing a new field (ctx) to store the current
boot mode in crrev/c/2944250 (ctx->bootmode), which will be leveraged
in both vboot flow and elog_add_boot_reason in coreboot.

In current steps of deciding bootmode, a function vb2ex_ec_trusted
is required. This function checks gpio EC_IN_RW pin and will return
'trusted' only if EC is not in RW. Therefore, we need to implement
similar utilities in coreboot.

We will deprecate vb2ex_ec_trusted and use the flag,
VB2_CONTEXT_EC_TRUSTED, in vboot, vb2api_fw_phase1 and set that flag
in coreboot, verstage_main.

Also add a help function get_ec_is_trusted which needed to be
implemented per mainboard.

BUG=b:177196147, b:181931817
BRANCH=none
TEST=Test on trogdor if manual recovery works

Signed-off-by: Hsuan Ting Chen <roccochen@chromium.org>
Change-Id: I479c8f80e45cc524ba87db4293d19b29bdfa2192
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57048
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/bootmode.h

@@ -11,6 +11,7 @@ int get_recovery_mode_retrain_switch(void);
 int clear_recovery_mode_switch(void);
 int get_wipeout_mode_switch(void);
 int get_lid_switch(void);
+int get_ec_is_trusted(void);
 
 /* Return 1 if display initialization is required. 0 if not. */
 int display_init_required(void);