elog: move MAX_EVENT_SIZE to commonlib/bsd/include

Moves MAX_EVENT_SIZE to commonlib/bsd/include, and renames it
ELOG_MAX_EVENT_SIZE to give it an "scoped" name.

The moving is needed because this defined will be used from
util/cbfstool (see next CL in the chain).

BUG=b:172210863
TEST=compiles Ok

Change-Id: I86b06d257dda5b325a8478a044045b2a63fb1a84
Signed-off-by: Ricardo Quesada <ricardoq@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/57394
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>

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

@@ -311,6 +311,9 @@ struct elog_event_extended_event {
 } __packed;
 
 
+/* Only the 7-LSB are used for size */
+#define ELOG_MAX_EVENT_SIZE                    0x7F
+
 enum cb_err elog_verify_header(const struct elog_header *header);
 const struct event_header *elog_get_next_event(const struct event_header *event);
 const void *event_get_data(const struct event_header *event);