net: phy: Refactor fwnode_get_phy_node()

Refactor to check if the fwnode we got is correct and return if so,
otherwise do additional checks. Using same pattern in all conditionals
makes it slightly easier to read and understand.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Link: https://patch.msgid.link/20250430143802.3714405-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>