reflect API changes in bladerf_rx.c

because bladerf_rx was removed and replaced by bladerf_sync_rx, we use
this function now. It assumes bladerf_sync_conf gets called before, so
do that.

TODO maybe bladerf_sync_conf should get its own matlab command, because
parameters are not ideal for every case (i guess).
remove pointer warnings in bladerf_fw_version.c

this removes unnccesary pointer related warnings. the warning for the
version-description string is kept as it may be more useful to allocate
an array of type string and strcpy() the version string in there. having
only the pointer is "pointless" in matlab.
reflect API changes in bladerf_get_lna_gain.c