pcm: hw: add a helper function to query status/control data

pcm: hw: add a helper function to query status/control data

When executing ioctl(2) with some commands, applications can request
ALSA PCM core to change appl_ptr in kernel space. Below is a list of
such operations:
 - SNDRV_PCM_IOCTL_PREPARE
 - SNDRV_PCM_IOCTL_RESET
 - SNDRV_PCM_IOCTL_REWIND
 - SNDRV_PCM_IOCTL_FORWARD
 - SNDRV_PCM_IOCTL_WRITEI_FRAMES
 - SNDRV_PCM_IOCTL_WRITEN_FRAMES
 - SNDRV_PCM_IOCTL_READI_FRAMES
 - SNDRV_PCM_IOCTL_READN_FRAMES

After these operations, the value of appl_ptr should be synchronized
between kernel/user spaces.

This commit adds a helper function to query status and control data
without issuing the control data just in fallback from failure of control
mapping.

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