fs/ntfs3: Keep preallocated only if option prealloc enabled

fs/ntfs3: Keep preallocated only if option prealloc enabled

commit e95113ed4d428219e3395044e29f5713fc446720 upstream.

If size of file was reduced, we still kept allocated blocks.
This commit makes ntfs3 work as other fs like btrfs.
Link: https://bugzilla.kernel.org/show_bug.cgi?id=214719
Fixes: 4342306f0f0d ("fs/ntfs3: Add file operations and implementation")
Reported-by: Ganapathi Kamath <hgkamath@hotmail.com>
Tested-by: Ganapathi Kamath <hgkamath@hotmail.com>
Reviewed-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>