crypto: loongson - add Loongson RNG driver support

crypto: loongson - add Loongson RNG driver support

Loongson's Random Number Generator is found inside Loongson Security
Engine chip.

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>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Link: https://lore.kernel.org/r/20250705072045.1067-3-zhaoqunqin@loongson.cn
Signed-off-by: Lee Jones <lee@kernel.org>