wifi: rt2x00: move up and reuse busy wait functions

Move bbp_ready and rf_ready busy wait functions up in the code so they
can more easily be used. Allow specifying register mask in rf_ready
function which is useful for calibration routines which will be added
in follow-up commits.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/3fdb9dc15e76a9f9c1948b4a3a1308a7a5677bb8.1663445157.git.daniel@makrotopia.org