mm: workingset: remove zero-seek setting for shadow node shrinker

zero-seek setting for shadow nodes will cause aggressive reclaim thus
removing more nodes from the working_set this would effect memstall
calculation of PSI, so keep the default seek settings.

Change-Id: Ib87ad5a07ef4c8ce42d078b99e1c2e5944e1899d
Signed-off-by: Vijayanand Jitta <vjitta@codeaurora.org>