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/security/vboot/vboot_logic.c

@@ -327,6 +327,9 @@ void verstage_main(void)
 	if (CONFIG(TPM_CR50))
 		check_boot_mode(ctx);
 
+	if (get_ec_is_trusted())
+		ctx->flags |= VB2_CONTEXT_EC_TRUSTED;
+
 	/* Do early init (set up secdata and NVRAM, load GBB) */
 	printk(BIOS_INFO, "Phase 1\n");
 	rv = vb2api_fw_phase1(ctx);