PCI: imx6: Consolidate redundant if-checks

Consolidated redundant if-checks pertaining to imx_pcie->phy. Instead of
two separate checks, merged them into one to improve code readability.

Link: https://lore.kernel.org/linux-pci/20240729-pci2_upstream-v8-8-b68ee5ef2b4d@nxp.com


Signed-off-by: Frank Li <Frank.Li@nxp.com>
[kwilczynski: commit log]
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>