Ignore return value of btsnd_hcic_* functions

btsnd_hcic_* functions return only true. This patch makes sure that no
logic is waiting for "false" value.
Few methods, that had their return value dependent on result of
btsnd_hcic_* were made void.

Test: unit tests pass
Change-Id: I43cff62f461ff35f4bd84e5338f1a587b6a05c58