riscv: fix reserved memory setup
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.79 by commit 518e49f0590de66555503aabe199ba8d3f2e24ac, it was introduced in version v5.4 by commit 922b0375fc93fb1a20c5617e37c389c26bbccb70. For more details please see the references link.