powerpc/fsl-lbc: Fix for fsl_upm

If Freescale LBC driver fails to initialise itself from device tree, then
internal structure is freed only but not NULL-fied.  As result functions
fsl_lbc_find() after checking the structure is not NULL are trying to
access device registers.
Signed-off-by: Alexandre Rusev <arusev@dev.rtsoft.ru>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

arch/powerpc/sysdev/fsl_lbc.c

@@ -328,6 +328,7 @@ static int __devinit fsl_lbc_ctrl_probe(struct platform_device *dev)
 err:
 	iounmap(fsl_lbc_ctrl_dev->regs);
 	kfree(fsl_lbc_ctrl_dev);
+	fsl_lbc_ctrl_dev = NULL;
 	return ret;
 }