mips: pci-mt7620: use dev_info() to log PCIe device detection result

Usually, We only need to print the error log when there is a PCIe card but
initialization fails. Whether the driver finds the PCIe card or not is the
expected behavior. So it's better to log these information with dev_info().

Tested on MT7628AN router Motorola MWR03.

Signed-off-by: Shiji Yang <yangshiji66@outlook.com>
Reviewed-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>