broadband-modem: increase default CPIN? timeout

The Telit LE922 seems to take just a bit more than 3s to reply. Let's
increase it up to 10s to be on the safe side.

  <debug> [1568385270.124866] (ttyUSB3): --> 'AT+CPIN?<CR>'
  <debug> [1568385273.396659] Couldn't check if unlock required: 'Serial command timed out'
  <warn>  [1568385273.396847] Modem couldn't be initialized: Couldn't check unlock status: Serial command timed out
  <info>  [1568385273.397009] Modem: state changed (unknown -> failed)
  <debug> [1568385273.397215] (ttyUSB3) device open count is 1 (close)
  <debug> [1568385273.397268] Creating ports context for SIM hot swap
  <debug> [1568385273.397289] (ttyUSB3) device open count is 2 (open)
  <debug> [1568385273.397309] (ttyUSB4) opening serial port...
  <debug> [1568385273.397676] (ttyUSB4): setting up baudrate: 57600
  <debug> [1568385273.397699] (ttyUSB4): no flow control explicitly requested for device
  <debug> [1568385273.397724] (ttyUSB4): port attributes not fully set
  <debug> [1568385273.397760] (ttyUSB4) device open count is 1 (open)
  <debug> [1568385273.397776] (ttyUSB4): running init sequence...
  <debug> [1568385273.397856] Extended signal information reporting disabled
  <debug> [1568385273.397927] Couldn't finish initialization in the current state: 'Modem is unusable, cannot fully initialize'
  <debug> [1568385273.398432] [device /sys/devices/pci0000:00/0000:00:14.0/usb1/1-11/1-11.4/1-11.4.1] exported modem at path '/org/freedesktop/ModemManager1/Modem/0'
  <debug> [1568385273.398464] [device /sys/devices/pci0000:00/0000:00:14.0/usb1/1-11/1-11.4/1-11.4.1]    plugin:  Telit
  <debug> [1568385273.398484] [device /sys/devices/pci0000:00/0000:00:14.0/usb1/1-11/1-11.4/1-11.4.1]    vid:pid: 0x1BC7:0x1040
  <debug> [1568385273.398509] (ttyUSB3) device open count is 1 (close)
  <debug> [1568385273.398546] (ttyUSB4): --> 'ATE0<CR>'
  <debug> [1568385273.400412] (ttyUSB3): <-- '<CR><LF>+CPIN: READY<CR><LF><CR><LF>OK<CR><LF>'
  <debug> [1568385273.404870] (ttyUSB4): <-- '<CR><LF>OK<CR><LF>'

src/mm-broadband-modem.c

@@ -1338,7 +1338,7 @@ modem_load_unlock_required (MMIfaceModem *self,
     mm_dbg ("checking if unlock required...");
     mm_base_modem_at_command (MM_BASE_MODEM (self),
                               "+CPIN?",
-                              3,
+                              10,
                               FALSE,
                               (GAsyncReadyCallback)cpin_query_ready,
                               task);