nb/intel: add IS_ENABLED() around Kconfig symbol references

Some of these can be changed from #if to if(), but that will happen
in a follow-on commmit.

Change-Id: Id5bc8b75b1fa372f31982b8636f1efa4975b61a5
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/20346
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>

src/northbridge/intel/i440bx/raminit.c

@@ -32,7 +32,7 @@ Macros and definitions.
 #define NB PCI_DEV(0, 0, 0)
 
 /* Debugging macros. */
-#if CONFIG_DEBUG_RAM_SETUP
+#if IS_ENABLED(CONFIG_DEBUG_RAM_SETUP)
 #define PRINT_DEBUG(x...)	printk(BIOS_DEBUG, x)
 #define DUMPNORTH()		dump_pci_device(NB)
 #else
@@ -301,7 +301,7 @@ static const u8 register_values[] = {
 	 *         0 = 3 clocks of RAS# precharge
 	 *         1 = 2 clocks of RAS# precharge
 	 */
-#if CONFIG_SDRAMPWR_4DIMM
+#if IS_ENABLED(CONFIG_SDRAMPWR_4DIMM)
 	SDRAMC + 0, 0x00, 0x10, /* The board has 4 DIMM slots. */
 #else
 	SDRAMC + 0, 0x00, 0x00, /* The board has 3 DIMM slots. */