drivers: gnss: lcx7g: Refactor power management

The implementation of power management did not account for
being on a power domain when initializing, and handling being
powered on and off at runtime.

The GNSS requires time to start up, which it always does when
powered on, before accepting commands. It also requires time
after resuming and suspending before accepting commands.

This commit implements this timeout, and improves logging to
make the power management more transparent, and removes some
redundant parenthesis for better readability.

Signed-off-by: Bjarki Arge Andreasen <bjarki@arge-andreasen.me>