Set_bandwidth on UHD called from osmosdr

The osmosdr source/sink blocks provide a “bandwidth” field, which
defaults to 0. Previously on B2xx this field would have no effect,
because up
until this point, the setting of the analog bandwidth on B2xx did
nothing. Now it does.

It looks like trying to set a bandwidth of 0 on B2xx clips to minimum
bandwidth (about 1MHz or so, from the resulting spectrum). Not sure what
the correct behavior here is. Should there be a magical numeric
value (perhaps 0) that means “set it to some sensible default, given the
sample-rate”, should users of the osmocom source blocks always just
set the bandwidth field to something like 0.8*sample-rate, and then
for hardware for which analog bandwidth is settable it will do
“something sensible”??

I don’t know what the correct answer is, just got caught by this with
one of my simple_ra users with a B200, and the very-latest UHD drivers.