When doing insert range and collapse range we should be
writing out the cached pages for the ranges affected but not
the whole file.

Fixes: c3a72bb2 ("smb3: Move the flush out of smb2_copychunk_range() into its callers")
Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (SUSE) <pc@cjr.nz>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>