[PATCH] OMAPDSS: fix return value check in create_dss_pdev()

* Wei Yongjun [off-list ref] [120920 23:29]:

From: Wei Yongjun <redacted>

In case of error, the function omap_device_alloc() returns ERR_PTR()
not NULL pointer. The NULL test in the return value check should
be replaced with IS_ERR().

Thanks applying into omap fixes.

Regards,

Tony