ALSA: line6: stop using get_seconds()

The get_seconds() function is deprecated because it truncates the
timestamp to 32 bits, so all users should change to ktime_get_seconds()
or ktime_get_real_seconds().

The firmware interface for passing the timestamp is also limited to
32 bits, so this patch only has the cosmetic effect of avoiding the
old interface.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>