mm: page_eject: Return right value during removal

hulk inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8K5CO



--------------------------------

Invalid value will be returned if there is no suitable pfn during
search, fix it.

Fixes: ecbd5d7c ("mm: page_eject: Introuduce page ejection")
Signed-off-by: Ma Wupeng <mawupeng1@huawei.com>