chromeec: Add google_chromeec_pd_get_amode

The google_chromeec_pd_get_amode API checks whether TCPM is in a
specified alternate mode or not.

BUG=b:72387533
BRANCH=none
TEST=See 23746 "mb/google/fizz: Wait until display is ready"

Change-Id: Ib9b4ad06b61326fa167c77758603e038d817f928
Signed-off-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-on: https://review.coreboot.org/23744
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

src/ec/google/chromeec/ec.h

@@ -36,6 +36,7 @@ u8 google_chromeec_get_event(void);
 bool google_chromeec_is_uhepi_supported(void);
 int google_ec_running_ro(void);
 void google_chromeec_init(void);
+int google_chromeec_pd_get_amode(uint16_t svid);
 
 /* Device events */
 uint64_t google_chromeec_get_device_enabled_events(void);