mfd: da9053: Ensure the FAULT_LOG is cleared during MFD driver probe

The function da9052_clear_fault_log() is added to mitigate the case of
persistent data being transferred between reboots.

Clearance of any the persistent information within the DA9053 FAULT_LOG
register must be completed during start-up so the fault-log does not
continue with previous values. A clearance function has been added here in
the kernel driver because wiping the fault-log cannot be counted on outside
the Linux kernel.

Signed-off-by: Steve Twiss <stwiss.opensource@diasemi.com>
Reviewed-by: Adam Thomson <adam.thomson.opensource@diasemi.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>