bsps/riscv: Fix warnings

c/src/lib/libbsp/riscv/riscv_generic/console/console-io.c

@@ -124,7 +124,6 @@ void console_initialize_hardware(void)
 static void outbyte_console(char ch)
 {
   htif_console_putchar(ch);
-  return 0;
 }
 
 static char inbyte_console(void)

c/src/lib/libbsp/riscv/riscv_generic/irq/irq.c

@@ -48,18 +48,13 @@ void bsp_interrupt_handler_default(rtems_vector_number vector)
 
 rtems_status_code bsp_interrupt_facility_initialize()
 {
-  /* TODO */
-  return 0;
+  return RTEMS_NOT_IMPLEMENTED;
 }
 
 void bsp_interrupt_vector_enable(rtems_vector_number vector)
 {
-  /* TODO */
-  return 0;
 }
 
 void bsp_interrupt_vector_disable(rtems_vector_number vector)
 {
-  /* TODO */
-  return 0;
 }