mfd: Add support for Loongson Security Engine chip controller

mfd: Add support for Loongson Security Engine chip controller

Loongson Security Engine chip supports RNG, SM2, SM3 and SM4 accelerator
engines. This is the base driver for other specific engine drivers.

Co-developed-by: Yinggang Gu <guyinggang@loongson.cn>
Signed-off-by: Yinggang Gu <guyinggang@loongson.cn>
Signed-off-by: Qunqin Zhao <zhaoqunqin@loongson.cn>
Reviewed-by: Huacai Chen <chenhuacai@loongson.cn>
Link: https://lore.kernel.org/r/20250705072045.1067-2-zhaoqunqin@loongson.cn
Signed-off-by: Lee Jones <lee@kernel.org>