mfd: atmel-hlcdc: Add Kconfig option description and name

The MFD_ATMEL_HLCDC was first intended to be selected by its sub-devices
but these sub-devices now depends on this option, we thus need to add
a name and a description so that users can see it.

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