Revert "drm/mipi-dsi: Fix detach call without attach"

This reverts commit 25eaa9f9 which is
commit 90d50b8d upstream.

It breaks the Android kernel abi and can be brought back in the future
in an abi-safe way if it is really needed.

Bug: 161946584
Change-Id: I7d11b085bf6cbe0d7eb1c0d87f5dc5c3cb88e323
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>