Use the new devm_of_phy_optional_get() helper instead of open-coding the
same operation.

As devm_of_phy_optional_get() returns NULL if either the PHY cannot be
found, or if support for the PHY framework is not enabled, it is no
longer needed to check for -ENODEV or -ENOSYS.

This lets us drop several checks for IS_ERR(), as phy_power_{on,off}()
handle NULL parameters fine.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Alan Stern <stern@rowland.harvard.edu>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Link: https://lore.kernel.org/r/3adc5dd1149a17ea7daf4463549feab886c6b145.1674584626.git.geert+renesas@glider.beSigned-off-by: Vinod Koul <vkoul@kernel.org>