core: Set EchoCancelingNoiseReduction to TRUE by default

core: Set EchoCancelingNoiseReduction to TRUE by default

According to Bluetooth HFP spec: By default, if the AG supports its
own embedded echo canceling and/or noise reduction functions, it shall
have them activated until the AT+NREC command is received. The
configuration set by the HF shall by used by the AG while the Service
Level Connection is active.

Since there isn't a command to query the current value, it is being
assumed that Echo Canceling and Noise Reduction is enabled when the
connection is established and the gateway supports this feature.