ALSA: pcxhr: convert timeval to ktime_t

This patch is concerned with migrating the time variables in the pcxhr
module found in the sound driver. The changes are concerend with the
y2038 problem where timeval will overflow in the year 2038. ktime_t
was used instead of timeval to get the wall time. The difference
is displayed now in nanoseconds instead of microseconds.

Signed-off-by: Aya Mahfouz <mahfouz.saif.elyazal@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>