Kernel/EFI: Add header for the RISC-V EFI boot protocol

These definitions are adapted from the UEFI spec to match our code
style.

Kernel/Firmware/EFI/Protocols/RISCVBootProtocol.h

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2024, Sönke Holz <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include <Kernel/Firmware/EFI/EFI.h>
+
+namespace Kernel::EFI {
+
+// RISCV_EFI_BOOT_PROTOCOL: https://github.com/riscv-non-isa/riscv-uefi/releases/download/1.0.0/RISCV_UEFI_PROTOCOL-spec.pdf
+struct RISCVBootProtocol {
+    static constexpr GUID guid = { 0xccd15fec, 0x6f73, 0x4eec, { 0x83, 0x95, 0x3e, 0x69, 0xe4, 0xb9, 0x40, 0xbf } };
+
+    using GetBootHartIDFn = EFIAPI Status (*)(RISCVBootProtocol*, FlatPtr* boot_hart_id);
+
+    u64 revision;
+    GetBootHartIDFn get_boot_hart_id;
+};
+static_assert(AssertSize<RISCVBootProtocol, 16>());
+
+}