mfd: atmel-hlcdc: Add support for new SoCs

Add the compatible strings for the at91sam9x5, at91sam9n12, sama5d4 and
sama5d2 SoCs.
Update the documentation accordingly.

Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>