phy: core: Reinstate pm_runtime_enabled() check in phy_pm_runtime_put()

On Koelsch (R-Car M2-W), during boot and s2ram:

    phy phy-e6590100.usb-phy-controller.0: Runtime PM usage count underflow!

While phy_pm_runtime_get{,_sync}() and phy_pm_runtime_put_sync() still
contain pm_runtime_enabled() checks, the same check in
phy_pm_runtime_put() was deemed redundant and removed, causing count
underflows with PHY drivers like drivers/phy/renesas/phy-rcar-gen2.c
that do not use Runtime PM yet,

Fix this by reinstating the check.

Fixes: caad07ae07 ("phy: core: Discard pm_runtime_put() return values")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://patch.msgid.link/3ca9f8166d21685bfbf97535da30172f74822130.1767107014.git.geert+renesas@glider.be
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/phy-core.c

@@ -195,6 +195,9 @@ void phy_pm_runtime_put(struct phy *phy)
 	if (!phy)
 		return;
 
+	if (!pm_runtime_enabled(&phy->dev))
+		return;
+
 	pm_runtime_put(&phy->dev);
 }
 EXPORT_SYMBOL_GPL(phy_pm_runtime_put);