serial: Remove extraneous SYS_MALLOC_F check

We enforce that DM_SERIAL will have SYS_MALLOC_F enabled and so
SYS_MALLOC_F_LEN will have a value.  Remove the build-time check.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/drivers/serial/serial-uclass.c b/drivers/serial/serial-uclass.c
index 8171b17..57a7848 100644
--- a/drivers/serial/serial-uclass.c
+++ b/drivers/serial/serial-uclass.c
@@ -27,10 +27,6 @@
  */
 static const unsigned long baudrate_table[] = CONFIG_SYS_BAUDRATE_TABLE;
 
-#if !CONFIG_VAL(SYS_MALLOC_F_LEN)
-#error "Serial is required before relocation - define CONFIG_$(SPL_)SYS_MALLOC_F_LEN to make this work"
-#endif
-
 #if CONFIG_IS_ENABLED(SERIAL_PRESENT)
 static int serial_check_stdout(const void *blob, struct udevice **devp)
 {