zte: fix warnings with -Wdiscarded-qualifiers
zte/mm-plugin-zte.c:54:7: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
54 | { "ATE0+CPMS?", 3, mm_port_probe_response_processor_is_at },
| ^~~~~~~~~~~~
zte/mm-plugin-zte.c:55:7: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
55 | { "ATE0+CPMS?", 3, mm_port_probe_response_processor_is_at },
| ^~~~~~~~~~~~
zte/mm-plugin-zte.c:56:7: error: initialization discards ‘const’ qualifier from pointer target type [-Werror=discarded-qualifiers]
56 | { "ATE0+CPMS?", 3, mm_port_probe_response_processor_is_at },
| ^~~~~~~~~~~~