drivers: gnss: remove sleep during init

It's not allowed to sleep during initialization of driver as called by
bg_thread_main --> z_sys_init_run_level(INIT_LEVEL_POST_KERNEL)
               --> do_device_init  -->  ubx_m10_init

There is no thread_base.timeout struct setup so far.

Signed-off-by: Andreas Klinger <ak@it-klinger.de>