ALSA: mtpav: Don't call card private_free at probe error path

The card destructor of nm256 driver does merely stopping the running
timer, and it's superfluous for the probe error handling.  Moreover,
calling this via the previous devres change would lead to another
problem due to the reverse call order.

This patch moves the setup of the private_free callback after the card
registration, so that it can be used only after fully set up.

Fixes: aa92050f

 ("ALSA: mtpav: Allocate resources with device-managed APIs")
Link: https://lore.kernel.org/r/20220412102636.16000-39-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>