Set coding in mncc_set_cause()

GSM 04.08 10.5.4.11

The Release indication needs to have the Coding Standard set.

For phones that would display a message on screen, such as
"Number not in use", if the coding standard is not defined,
the display may show "Error in Connection"

Change-Id: Ib28b62a41d433e231cff5910d19455296b284df6
3 files changed