drivers: modem: gsm: Fix to COPS cmd parse info

drivers: modem: gsm: Quectel EC21 and BG9x act as a gsm modem without
problem, but COPS commands can returns just one value with 'mode'.

Format and oper are not mandatory. This modification reads 'mode'.
Also a modification on modem_cmd_read_cops_cmd is needed.

Signed-off-by: Jair Jack <jack@icatorze.com.br>
1 file changed