staging: mt7621-pci: rename 'mt7621_pcie_enable_port' into 'mt7621_pcie_init_port'

Rename function 'mt7621_pcie_enable_port' with a name which is better
for what the function is really doing calling it 'mt7621_pcie_init_port'.

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