mm: Fix is_zero_page() usage in try_grab_page()

The backport of upstream commit c8070b78 ("mm: Don't pin ZERO_PAGE
in pin_user_pages()") into v6.1.130 noted below in Fixes does not
account for commit 0f089235 ("mm: allow multiple error returns in
try_grab_page()"), which changed the return value of try_grab_page()
from bool to int.  Therefore returning 0, success in the upstream
version, becomes an error here.  Fix the return value.

Fixes: 476c1dfe ("mm: Don't pin ZERO_PAGE in pin_user_pages()")
Link: https://lore.kernel.org/all/Z_6uhLQjJ7SSzI13@eldamar.lan


Reported-by: Salvatore Bonaccorso <carnil@debian.org>
Reported-by: Milan Broz <gmazyland@gmail.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: stable@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>