ALSA: core: add .get_time_info

Introduce more generic .get_time_info to retrieve
system timestamp and audio timestamp in single routine.
Backwards compatibility is preserved with same functionality
as with .wall_clock method (to be removed in following commits
to avoid breaking git bisect)

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

diff --cc include/sound/pcm.h
Simple merge

diff --cc sound/core/pcm_lib.c
Simple merge

diff --cc sound/core/pcm_native.c
Simple merge