staging: mt7621-pci-phy: prevent use of uninitialized variable

Do not use uninitialized variable 'port' when printing an error message

Signed-off-by: Antti Keränen <detegr@gmail.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>