pci_mmio_cfg.h: Add a compile time error if MMCONF_BASE_ADDRESS is undefined

if CONFIG_MMCONF_SUPPORT is set, add a compiletime error if
CONFIG_MMCONF_BASE_ADDRESS is not defined.

Change-Id: I0439e994d170e8ec564ce188e82a850e2a286a66
Signed-off-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/35883
Reviewed-by: Nico Huber <nico.h@gmx.de>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/device/pci_mmio_cfg.h

@@ -90,6 +90,10 @@ void pci_mmio_write_config32(pci_devfn_t dev, uint16_t reg, uint32_t value)
 
 #if CONFIG(MMCONF_SUPPORT)
 
+#if CONFIG_MMCONF_BASE_ADDRESS == 0
+#error "CONFIG_MMCONF_BASE_ADDRESS undefined!"
+#endif
+
 /* Avoid name collisions as different stages have different signature
  * for these functions. The _s_ stands for simple, fundamental IO or
  * MMIO variant.