flex_array: fix the panic when calling flex_array_alloc() without __GFP_ZERO

flex_array: fix the panic when calling flex_array_alloc() without __GFP_ZERO

commit e59464c735db19619cde2aa331609adb02005f5b upstream.

memset() is called with the wrong address and the kernel panics.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
Cc: Patrick McHardy <kaber@trash.net>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>