[MIPS] Update pnx8550-v2pci_defconfig

In the current pnx8550-v2pci_defconfig CONFIG_SGI_IP22 has been selected.
Signed-off-by: NYoichi Yuasa <yoichi_yuasa@tripeaks.co.jp>
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>