PCI: dwc: pci-dra7xx: Fix runtime PM imbalance on error

pm_runtime_get_sync() increments the runtime PM usage counter even
it returns an error code. Thus a pairing decrement is needed on
the error handling path to keep the counter balanced.

Link: https://lore.kernel.org/r/20200520084756.31620-1-dinghao.liu@zju.edu.cn


Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>