pcm: hw: allocate fallback buffer in advance of trials of mapping

pcm: hw: allocate fallback buffer in advance of trials of mapping

When allowing failure of map operation for both of status/control data
for runtime of PCM substream, applications need to use fallback buffer
for an alternative ioctl. However, in current implementation, status
mapping is dominant to the allocation.

This commit moves code for the allocation outside of the mapping
operation for status data.

Signed-off-by: Takashi Sakamoto <o-takashi@sakamocchi.jp>
Signed-off-by: Takashi Iwai <tiwai@suse.de>