PCI: mt7621: Allow COMPILE_TEST for all arches

Since all MIPS-specific code has been removed from driver, allow it to be
enabled for COMPILE_TEST on all architectures.

Mark it as tristate and remove MIPS the MIPS dependency.
Signed-off-by: Sergio Paracuellos <sergio.paracuellos@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/Kconfig

@@ -333,7 +333,7 @@ config PCIE_APPLE
 
 config PCIE_MT7621
 	tristate "MediaTek MT7621 PCIe Controller"
-	depends on (RALINK && SOC_MT7621) || (MIPS && COMPILE_TEST)
+	depends on SOC_MT7621 || COMPILE_TEST
 	select PHY_MT7621_PCI
 	default SOC_MT7621
 	help