PatchPanel: Fix typo in patch validation

This piece of logic does not seem to be correct:

(patch->sinks[i].type == AUDIO_PORT_TYPE_MIX ||
 patch->sinks[i].ext.mix.hw_module != srcModule)

I assume it should be:

(patch->sinks[i].type == AUDIO_PORT_TYPE_MIX ||
    (patch->sinks[i].type == AUDIO_PORT_TYPE_DEVICE &&
     patch->sinks[i].ext.device.hw_module != srcModule)

Was working fine because 'hw_module' is the first field both
in audio_port_config_device_ext and audio_port_config_mix_ext.

Test: make
Change-Id: Icf80cec701048bddc4d63eaedf00fc75b5b891dd