drivers: gnss: api: Remove periodic configuration

The GNSS device driver API includes an API for setting the periodic
power configuration at runtime. This API is not used in-tree, and is
antithetical to the pm device subsystem.

The periodic config configures the GNSS to search for a fix for a
given amount of time, then suspend itself for a given amount of time,
and repeat this pattern. The issue with this is that both the
application and the GNSS modem itself can be in a conflicting power
state, where the device is resumed (pm device), but actually suspended.

Applications which wish to periodically resume/suspend the modem, even
in more sophisticated ways like suspended after first fix, can simply
implement this logic, using the pm_device calls and the GNSS callbacks.

Signed-off-by: Bjarki Arge Andreasen <bjarki.andreasen@nordicsemi.no>