drivers: modem: socket: add wait_data and data_ready functions

Let's hide the internals of the modem_socket's sem_data_ready and
poll handling with 2 new functions:
- modem_socket_wait_data: take a semaphore and wait for data
- modem_socket_data_ready: give back the data ready semaphore and
  unblock poll() users

Signed-off-by: Michael Scott <mike@foundries.io>
2 files changed