target/platform: mdmfermium: change to support UART5

Change the UART base and GPIO numbers to support
UART5 on mdmfermium target.

Change-Id: I412fb2e919955800ccc17fb7d18879100070279f
diff --git a/target/mdmfermium/init.c b/target/mdmfermium/init.c
index 1ccc227..98ac6e8 100644
--- a/target/mdmfermium/init.c
+++ b/target/mdmfermium/init.c
@@ -118,7 +118,7 @@
 void target_early_init(void)
 {
 #if WITH_DEBUG_UART
-	uart_dm_init(1, 0, BLSP1_UART1_BASE);
+	uart_dm_init(1, 0, BLSP1_UART5_BASE);
 #endif
 }