libgloss/riscv: Fix struct utimbuf warning in sys_utime.c stub

Include <utime.h> to ensure 'struct utimbuf' is visible. This fixes a
compiler warning where the struct was declared inside the parameter
list.

Signed-off-by: Pincheng Wang <[email protected]>

Author: wpcwzy

libgloss/riscv/sys_utime.c

@@ -1,4 +1,6 @@
 #include <machine/syscall.h>
+#include <sys/types.h>
+#include <utime.h>
 
 /* Stub.  */
 int