staging, mt7621-pci: fix build without pci support

[ Upstream commit 90cd9bed5adb3e3bd4d3ac4cbcecbc4a8028bbaf ]

Add depends on PCI for PCI_MT7621

Signed-off-by: Maxim Zhukov <mussitantesmortem@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin (Microsoft) <sashal@kernel.org>