ble_hs_hci_read_chan_map() function

Queries the controller for the channel map used with the specified connection. The channel map is represented as an array of five bytes, with each bit corresponding to an individual channel. The array is interpreted as little-endian, such that: map[0] & 0x01 --> Channel 0. map[0] & 0x02 --> Channel 1. ... map[1] & 0x01 --> Channel 8. As there are 37 channels, only the first 37 bits get written. If a bit is 1, the corresponding channel is used. Otherwise, the channel is unused.