PCI: endpoint: pci-epf-vntb: Fix typo in comments

Replace "Span" with "Spad".

Link: https://lore.kernel.org/r/20221214172254.668282-1-Frank.Li@nxp.com


Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Manivannan Sadhasivam <mani@kernel.org>