src/ec/intel: Create common code for board_id implementation

This patch creates initial common code structure for board_id
implementation for intel rvp platforms. Board_id helps in
identifying the platform with respect to CHROME_EC and INTEL_EC
(Windows_EC). Changes include
1. Create initial board_id.c and board_id.h
2. Modify the Makefile to include src/ec/intel directory

BUG=b:260654043
TEST=Able to build with the patch and boot the mtlrvp platform with the
subsequent patches in the train

Signed-off-by: Harsha B R <harsha.b.r@intel.com>
Change-Id: If133f6a72b8c3e1d8811a11f91e4556beb8c16e0
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70227
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Usha P <usha.p@intel.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/ec/intel/Makefile.inc

@@ -0,0 +1,7 @@
+## SPDX-License-Identifier: GPL-2.0-or-later
+
+bootblock-y += board_id.c
+romstage-y += board_id.c
+ramstage-y += board_id.c
+
+CPPFLAGS_common += -I$(src)/ec/intel

src/ec/intel/board_id.c

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <boardid.h>
+#include "board_id.h"
+
+/* Get RVP Board ID */
+int get_rvp_board_id(void)
+{
+	return BOARD_ID_INIT;
+}

src/ec/intel/board_id.h

@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#ifndef _MAINBOARD_COMMON_BOARD_ID_H_
+#define _MAINBOARD_COMMON_BOARD_ID_H_
+
+/* Returns RVP board_id */
+int get_rvp_board_id(void);
+
+#endif /* _MAINBOARD_COMMON_BOARD_ID_H_ */