serial: Remove CONFIG_SERIAL_MULTI from remaining sources

Remove the parts depending either on disabled CONFIG_SERIAL_MULTI
or ifdefs around CONFIG_SERIAL_MULTI parts since CONFIG_SERIAL_MULTI
is now enabled by default.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Marek Vasut <marek.vasut@gmail.com>
Cc: Tom Rini <trini@ti.com>
Cc: Anatolij Gustschin <agust@denx.de>
Cc: Stefan Roese <sr@denx.de>
diff --git a/common/fdt_support.c b/common/fdt_support.c
index 593f16c..963ea90 100644
--- a/common/fdt_support.c
+++ b/common/fdt_support.c
@@ -94,7 +94,7 @@
 
 #ifdef CONFIG_OF_STDOUT_VIA_ALIAS
 
-#ifdef CONFIG_SERIAL_MULTI
+#ifdef CONFIG_CONS_INDEX
 static void fdt_fill_multisername(char *sername, size_t maxlen)
 {
 	const char *outname = stdio_devices[stdout]->name;
@@ -106,9 +106,7 @@
 	if (strcmp(outname + 1, "serial") > 0)
 		strncpy(sername, outname + 1, maxlen);
 }
-#else
-static inline void fdt_fill_multisername(char *sername, size_t maxlen) {}
-#endif /* CONFIG_SERIAL_MULTI */
+#endif
 
 static int fdt_fixup_stdout(void *fdt, int chosenoff)
 {