fbdev: omapfb: panel-tpo-td043mtea1: fix error code in probe()

This was using the wrong variable, "r", instead of "ddata->vcc_reg", so
it returned success instead of a negative error code.

Fixes: 0d3dbeb8

 ("video: fbdev: omapfb: panel-tpo-td043mtea1: Make use of the helper function dev_err_probe()")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Helge Deller <deller@gmx.de>