ALSA: hda: Fix krealloc() with __GFP_ZERO usage

ALSA: hda: Fix krealloc() with __GFP_ZERO usage

BugLink: http://bugs.launchpad.net/bugs/1615620
commit 33baefe5e72f17a6df378e48196cd8cada11deec upstream.

krealloc() doesn't work always properly with __GFP_ZERO flag as
expected.  For clearing the reallocated area, we need to clear
explicitly instead.

Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>