efi_loader: Enable RISCV_EFI_BOOT_PROTOCOL support

This adds support for new RISCV_EFI_BOOT_PROTOCOL to
communicate the boot hart ID to bootloader/kernel on RISC-V
UEFI platforms.

The specification of the protocol is hosted at:
https://github.com/riscv-non-isa/riscv-uefi

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
index 24f9a2b..e5e35fe 100644
--- a/lib/efi_loader/Kconfig
+++ b/lib/efi_loader/Kconfig
@@ -369,4 +369,14 @@
 	help
 	  Enabling this option creates the ESRT UEFI system table.
 
+config EFI_RISCV_BOOT_PROTOCOL
+	bool "RISCV_EFI_BOOT_PROTOCOL support"
+	default y
+	depends on RISCV
+	help
+	  The EFI_RISCV_BOOT_PROTOCOL is used to transfer the boot hart ID
+	  to the next boot stage. It should be enabled as it is meant to
+	  replace the transfer via the device-tree. The latter is not
+	  possible on systems using ACPI.
+
 endif