ARM: rockchip: pm: Fix PTR_ERR() argument

PTR_ERR should access the value just tested by IS_ERR.

The semantic patch that makes this change is available
in scripts/coccinelle/tests/odd_ptr_err.cocci.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Signed-off-by: Heiko Stuebner <heiko@sntech.de>