sierra: disable CPOL in the GL7600
Similar to the EM7345 (also from Sierra Wireless), the GL7600 becomes unresponsive after using "AT+CPOL?".
Fixes #595 (closed)
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Similar to the EM7345 (also from Sierra Wireless), the GL7600 becomes unresponsive after using "AT+CPOL?".
Fixes #595 (closed)