mt76x0: pci: fix set external PA I/O current

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/net/wireless/mediatek/mt76/mt76x0/pci.c: In function 'mt76x0e_register_device':
drivers/net/wireless/mediatek/mt76/mt76x0/pci.c:107:8: warning:
 variable 'data' set but not used [-Wunused-but-set-variable]

It seems correct value to write is 'data'

Fixes: 2b2cb40b ("mt76x0: pci: add hw initialization at bootstrap")
Acked-by: Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Felix Fietkau <nbd@nbd.name>