LU-8402 llite: simplify ll_inode_revalidate()

LU-8402 llite: simplify ll_inode_revalidate()

ll_inode_revalidate() is only called by ll_getattr() so move the
contents of ll_inode_revalidate() to ll_getattr() and rename
__ll_inode_revalidate() to ll_inode_revalidate().

Signed-off-by: John L. Hammond <john.hammond@intel.com>
Change-Id: Ieeba1b74551b7a531e1db47ccb0638c72c90adb6
Reviewed-on: https://review.whamcloud.com/30036
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Dmitry Eremin <dmitry.eremin@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>