staging: tidspbridge: remove disp_init() and disp_exit()

The disp module has a disp_init() and a disp_exit() whose only purpose
is to keep a reference counting which is not used at all.

This patch removes these functions and the reference count variable.

There is no functional changes.

Signed-off-by: Víctor Manuel Jáquez Leal <vjaquez@igalia.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>