PCI: rcar: Shut the PHY down in failpath

If anything fails past phy_init_fn() and the system is a Gen3 with
a PHY, the PHY will be left on and inited. This is caused by the
phy_init_fn, which is in fact a pointer to rcar_pcie_phy_init_gen3()
function, which starts the PHY, yet has no counterpart in the failpath.
Add that counterpart.

Fixes: 517ca93a ("PCI: rcar: Add R-Car gen3 PHY support")
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Simon Horman <horms+renesas@verge.net.au>
Cc: Geert Uytterhoeven <geert+renesas@glider.be>
Cc: Phil Edworthy <phil.edworthy@renesas.com>
Cc: Wolfram Sang <wsa@the-dreams.de>