PCI: endpoint: pci-epf-vntb: Fix struct epf_ntb_ctrl indentation

Align the indentation of struct epf_ntb_ctrl with other structs in
the driver.

Link: https://lore.kernel.org/r/20221102141014.1025893-3-Frank.Li@nxp.comSigned-off-by: NFrank Li <frank.li@nxp.com>
Signed-off-by: NLorenzo Pieralisi <lpieralisi@kernel.org>