mfd: max77620: Fix swapped FPS_PERIOD_MAX_US values

The FPS_PERIOD_MAX_US definitions are swapped for MAX20024 and MAX77620,
fix it.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>