drivers: 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/drivers/mtd/spi/Makefile b/drivers/mtd/spi/Makefile
index 4093953..2a287a6 100644
--- a/drivers/mtd/spi/Makefile
+++ b/drivers/mtd/spi/Makefile
@@ -6,7 +6,7 @@
 obj-$(CONFIG_$(SPL_TPL_)DM_SPI_FLASH) += sf-uclass.o
 spi-nor-y := sf_probe.o spi-nor-ids.o
 
-ifdef CONFIG_SPL_BUILD
+ifdef CONFIG_XPL_BUILD
 obj-$(CONFIG_SPL_SPI_BOOT)	+= fsl_espi_spl.o
 ifeq ($(CONFIG_$(SPL_TPL_)SPI_FLASH_TINY),y)
 spi-nor-y += spi-nor-tiny.o