mm/swapfile: remove pr_debug in get_swap_pages()

It's known that get_swap_pages() may fail to find available space under
some extreme case, but pr_debug() provides useless information.  Let's
remove it.

Link: https://lkml.kernel.org/r/20230131071035.1085968-1-xialonglong1@huawei.com


Signed-off-by: Longlong Xia <xialonglong1@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Chen Wandun <chenwandun@huawei.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Nanyong Sun <sunnanyong@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>