New define is available since libosmocore 1.1.0, and we already require
1.3.0, so no need to update dependenices.
Let's change it to avoid people re-using old BSC_FD_* symbols when
copy-pasting somewhere else.
Change-Id: I269690c1c9e4d19b5b69eef206b95e71f7931188
Use the new macros to deal with little/big endian. Im a bit
worried to make this change due the little test coverage in
this module but in case of a typo the elements would not be
defined.