mm/zbud: remove redundant initialization

zhdr is already initialized in the front of the function, so remove
redundant initialization here.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Seth Jennings <sjenning@redhat.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Link: https://lkml.kernel.org/r/1600419885-191907-1-git-send-email-chenxiang66@hisilicon.com


Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>