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

This reverts commit 3cdc6444 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: Icadd1f376dcf40c38d733025b32bcfc8f10e2caa
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>