xfs: convert to ctime accessor functions

xfs: convert to ctime accessor functions

Source kernel commit: a0a415e34b57368acd262e1172720252c028b936

In later patches, we're going to change how the inode's ctime field is
used. Switch to using accessor functions instead of raw accesses of
inode->i_ctime.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Message-Id: <20230705190309.579783-80-jlayton@kernel.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>