staging: bcm2835-audio: Set SNDRV_PCM_INFO_SYNC_APPLPTR

The recent ALSA PCM core supports the SNDRV_PCM_INFO_SYNC_APPLPTR flag
indicating that the driver needs the ack call at each appl_ptr
update.  This is requirement for the indirect PCM implementations like
bcm2835-audio driver, too.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>