soc: sunxi: sram: Save a pointer to the OF match data

It is inefficient to match the compatible string every time the regmap
is accessed.

Acked-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Samuel Holland <samuel@sholland.org>
Reviewed-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Link: https://lore.kernel.org/r/20220815041248.53268-9-samuel@sholland.org


Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>