PCI: tegra: Fix return value check of pm_runtime_get_sync()

PCI: tegra: Fix return value check of pm_runtime_get_sync()

pm_runtime_get_sync() returns the device's usage counter. This might
be >0 if the device is already powered up or CONFIG_PM is disabled.

Abort probe function on real error only.

Fixes: da76ba50963b ("PCI: tegra: Add power management support")
Link: https://lore.kernel.org/r/20191216111825.28136-1-david.engraf@sysgo.com
Signed-off-by: David Engraf <david.engraf@sysgo.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Andrew Murray <andrew.murray@arm.com>
Cc: stable@vger.kernel.org	# v4.17+