elog: Define constant for RW region name

This CL indroduces the ELOG_RW_REGION_NAME. This constant replaced the
hardcoded "RW_ELOG" value. This constant will be used also by elogtool
(see CL in the commit chain).

BUG=b:172210863

Change-Id: Ie8d31204e65fd67d52b0f8ced7b8c1ffdcf5b539
Signed-off-by: Ricardo Quesada <ricardoq@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/56986
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/commonlib/bsd/include/commonlib/bsd/elog.h

@@ -18,6 +18,7 @@ struct elog_header {
 /* ELOG related constants */
 #define ELOG_SIGNATURE			0x474f4c45  /* 'ELOG' */
 #define ELOG_VERSION			1
+#define ELOG_RW_REGION_NAME		"RW_ELOG"
 
 /* SMBIOS event log header */
 struct event_header {