google/edgar: add new board as variant of cyan baseboard

Add support for google/edgar (Acer Chromebook 14 CB3-431) as
a variant of the cyan Braswell basebaseboard.

- Add board-specific code as the new edgar variant
- Add common code to the baseboard which will apply to all
  variants other than cyan

Sourced from Chromium branch firmware-edgar-7287.167.B,
commit 2319742: Edgar: Add Micron MT52L256M32D1PF-107 SPD data

Change-Id: I58548cbbc85828f37c0023e8aa9e09bdca612659
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/21127
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin Roth <martinroth@google.com>

src/mainboard/google/cyan/smihandler.c

@@ -152,6 +152,11 @@ void mainboard_smi_sleep(uint8_t slp_typ)
 	/* Clear pending events that may trigger immediate wake */
 	while (google_chromeec_get_event() != 0)
 		;
+
+	/* Set LPC lines to low power in S3/S5. */
+	if ((slp_typ == ACPI_S3) || (slp_typ == ACPI_S5)) {
+		lpc_set_low_power();
+	}
 #endif
 }