refactor(measured boot): rename a macro INVALID_ID to EVLOG_INVALID_ID

Renamed a macro 'INVALID_ID' to 'EVLOG_INVALID_ID' to avoid its clash
with other macro names and to show it is explicitly used for Event
Log driver.

Change-Id: Ie4c92b3cd1366d9a59cd6f43221e24734865f427
Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com>
diff --git a/drivers/measured_boot/event_log/event_log.c b/drivers/measured_boot/event_log/event_log.c
index 1755dd9..52ed278 100644
--- a/drivers/measured_boot/event_log/event_log.c
+++ b/drivers/measured_boot/event_log/event_log.c
@@ -250,11 +250,11 @@
 	const event_log_metadata_t *metadata_ptr = plat_metadata_ptr;
 
 	/* Get the metadata associated with this image. */
-	while ((metadata_ptr->id != INVALID_ID) &&
+	while ((metadata_ptr->id != EVLOG_INVALID_ID) &&
 		(metadata_ptr->id != data_id)) {
 		metadata_ptr++;
 	}
-	assert(metadata_ptr->id != INVALID_ID);
+	assert(metadata_ptr->id != EVLOG_INVALID_ID);
 
 	/* Calculate hash */
 	rc = crypto_mod_calc_hash((unsigned int)MBEDTLS_MD_ID,