dt-bindings: mfd: Add bindings for DA9063L

Add device tree bindings for the Dialog DA9063L. This is a
variant of the DA9063 chip with smaller package, with less
LDO regulators and without RTC block. The other properties
of the chip are the same, including the content of the chip
ID register.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>