net: mdio: Use of_property_count_u32_elems() to get property length

Replace of_get_property() with the type specific
of_property_count_u32_elems() to get the property length.

This is part of a larger effort to remove callers of of_get_property()
and similar functions. of_get_property() leaks the DT property data
pointer which is a problem for dynamically allocated nodes which may
be freed.

Signed-off-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20240731201514.1839974-2-robh@kernel.org


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