RISC-V: Free-up initrd in free_initrd_mem()

We should free-up initrd memory in free_initrd_mem() instead
of doing nothing.
Signed-off-by: NAnup Patel <anup.patel@wdc.com>
Reviewed-by: NMike Rapoport <rppt@linux.ibm.com>

arch/riscv/mm/init.c

@@ -94,8 +94,9 @@ static void __init setup_initrd(void)
 	initrd_end = 0;
 }
 
-void free_initrd_mem(unsigned long start, unsigned long end)
+void __init free_initrd_mem(unsigned long start, unsigned long end)
 {
+	free_reserved_area((void *)start, (void *)end, -1, "initrd");
 }
 #endif /* CONFIG_BLK_DEV_INITRD */