staging: sm750fb: disable PCI device if lynxfb_pci_probe fails

In case of error during lynxfb_pci_probe, the function returned without
calling pci_disable_device. Fix it by adding pci_disable_device on the
error cleanup path.

Signed-off-by: Mike Rapoport <mike.rapoport@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>