mb/siemens/mc_apl1/mainboard.c: Refactor loop body

Break down multi-line compound conditions into multiple if-statements,
and leverage `continue` statements to avoid nesting multiple checks.

Change-Id: I5edc279a57e25a0dff1a4b42f0bbc88c0659b476
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/47403
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Tested-by: siemens-bot
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Uwe Poeche <uwe.poeche@siemens.com>
diff --git a/src/mainboard/siemens/mc_apl1/mainboard.c b/src/mainboard/siemens/mc_apl1/mainboard.c
index 0d93563..5b8f70f 100644
--- a/src/mainboard/siemens/mc_apl1/mainboard.c
+++ b/src/mainboard/siemens/mc_apl1/mainboard.c
@@ -85,19 +85,18 @@
 	/* Open main hwinfo block */
 	if (hwilib_find_blocks("hwinfo.hex") != CB_SUCCESS)
 		return CB_ERR;
-	/* Now try to find a valid MAC address in hwinfo for this mapping.*/
+	/* Now try to find a valid MAC address in hwinfo for this mapping. */
 	for (i = 0; i < MAX_NUM_MAPPINGS; i++) {
-		if ((hwilib_get_field(XMac1Mapping + i, buf, 16) == 16) &&
-			!(memcmp(buf, mapping, chain_len + 4))) {
-		/* There is a matching mapping available, get MAC address. */
-			if ((hwilib_get_field(XMac1 + i, mac, 6) == 6) &&
-			    (is_mac_adr_valid(mac))) {
-				return CB_SUCCESS;
-			} else {
-				return CB_ERR;
-			}
-		} else
+		if (hwilib_get_field(XMac1Mapping + i, buf, 16) != 16)
 			continue;
+		if (memcmp(buf, mapping, chain_len + 4))
+			continue;
+		/* There is a matching mapping available, get MAC address. */
+		if (hwilib_get_field(XMac1 + i, mac, 6) == 6) {
+			if (is_mac_adr_valid(mac))
+				return CB_SUCCESS;
+		}
+		return CB_ERR;
 	}
 	/* No MAC address found for */
 	return CB_ERR;