samples: drivers: video: capture: change log verbosity

Increase log verbosity to print one line per captured frames and make
it like in the README by default. This avoids giving the impression
that the capture sample does not work. Users desiring to get better
performance can disable logging or reduce verbosity from INF to WRN.

Signed-off-by: Josuah Demangeon <me@josuah.net>