Revert "drm/panel: Initialise panel dev and funcs through drm_panel_init()"

This reverts commit 362940f8 which is
commit 6dbe0c4b0fc0646442b2b1580d022404e582fd7b upstream.

It breaks the Android abi and is not needed for any Android systems.  If
it is required in the future, it can come back in an abi-safe way.

Bug: 161946584
Change-Id: I4df07557f05d05ef1d0762a5392ed7203894fb56
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>