Preparing to add Loongson-3 machine support, add Loongson-3's LEFI (a
UEFI-like interface for BIOS-Kernel boot parameters) helpers first.

Co-developed-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Signed-off-by: Huacai Chen <chenhuacai@kernel.org>
Signed-off-by: Jiaxun Yang <jiaxun.yang@flygoat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-Id: <20201221110538.3186646-4-chenhuacai@kernel.org>
[PMD: Fixed typo]
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>