phy: core: properly handle failure of pm_runtime_get functions

In case pm_runtime_get*() fails, it still
increments pm usage counter, so we *must*
make sure to pm_runtime_put() even in those
cases.

This patch fixes that mistake the same way
usbcore treats those possible failures.

Signed-off-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>