staging: mt7621-pci: rename RALINK_PCI_CONFIG_DATA_VIRTUAL_REG definition

RALINK_PCI_CONFIG_DATA_VIRTUAL_REG is a very long name. Make it a bit
shorter renaming it to RALINK_PCI_CONFIG_DATA.

Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Tested-by: NeilBrown <neil@brown.name>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>