arch: Use CONFIG_XPL_BUILD instead of CONFIG_SPL_BUILD

Use the new symbol to refer to any 'SPL' build, including TPL and VPL

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/include/asm/arch-lpc32xx/sys_proto.h b/arch/arm/include/asm/arch-lpc32xx/sys_proto.h
index 4675dc3..b499d97 100644
--- a/arch/arm/include/asm/arch-lpc32xx/sys_proto.h
+++ b/arch/arm/include/asm/arch-lpc32xx/sys_proto.h
@@ -16,7 +16,7 @@
 void lpc32xx_i2c_init(unsigned int devnum);
 void lpc32xx_ssp_init(void);
 void lpc32xx_usb_init(void);
-#if defined(CONFIG_SPL_BUILD)
+#if defined(CONFIG_XPL_BUILD)
 void ddr_init(const struct emc_dram_settings *dram);
 #endif
 #endif /* _LPC32XX_SYS_PROTO_H */