ALSA: Fix invalid jiffies check after pause

The hw_ptr_jiffies has to be reset properly to avoid the invalid
check of jiffies delta in snd_pcm_update_hw_ptr*() functions.
Especailly this patch fixes the bogus jiffies check after the puase
and resume.

This patch is a modified version of the original patch by Jaroslav.

Signed-off-by: Takashi Iwai <tiwai@suse.de>