mfd: lp87565: Add LP87524-Q1 variant

Add support for the LP87524B/J/P-Q1 Four 4-MHz Buck Converter. This is a
variant of the LP87565 having 4 single-phase outputs and up to 10 A of
total output current.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Lee Jones <lee.jones@linaro.org>