max31760: Maxim Fan Controller Driver

This adds support for Maxim(MAX31760) Fan Controller.
Enables and runs the fan at 25Khz by default.

Change-Id: I6553f4846e0420c80aaabd611510baa756871cdf
Signed-off-by: Rajesh Bharathwaj <rajeshbharathwaj@codeaurora.org>