Currently DAPM has a lot of similar code to handle errors from
snd_soc_dapm_new_control_unlocked, and much of this code does
not really accurately reflect what the function returns.

Firstly, most places will check for a return value of
-EPROBE_DEFER and silence any error messages in that case. The
one notable exception here being dapm_kcontrol_data_alloc
which does currently print any error messages in the case
of snd_soc_dapm_new_control_unlocked returning NULL or an
error. Additionally the error prints being silenced in these
case are redundant as snd_soc_dapm_new_control_unlocked can
only return -EPROBE_DEFER or NULL when failing.

Secondly, most places will treat a return value of NULL as
an -ENOMEM.  This is not correct either since any error except
EPROBE_DEFER will cause a return value of NULL from
snd_soc_dapm_new_control_unlocked.

Centralise this handling and the error messages within
snd_soc_dapm_new_control_unlocked and update the callers
to simply check IS_ERR and return. Note that this update is
slightly simpler in the case of dapm_kcontrol_data_alloc where
that is fairly close to the handling that was already in place.
Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Mark Brown <broonie@kernel.org>