PCI: histb: Fix an error handling path in histb_pcie_probe()

If an error occurs after a successful phy_init() call, then phy_exit()
should be called.

Add the missing call, as already done in the remove function.

Fixes: bbd11bdd ("PCI: hisi: Add HiSilicon STB SoC PCIe controller driver")
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
[kwilczynski: remove unnecessary hipcie->phy NULL check from
histb_pcie_probe() and squash a patch that removes similar NULL
check for hipcie-phy from histb_pcie_remove() from
https://lore.kernel.org/linux-pci/c369b5d25e17a44984ae5a889ccc28a59a0737f7.1742058005.git.christophe.jaillet@wanadoo.fr

]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Link: https://lore.kernel.org/r/8301fc15cdea5d2dac21f57613e8e6922fb1ad95.1740854531.git.christophe.jaillet@wanadoo.fr