global: Rename SPL_ to XPL_

Use XPL_ as the symbol to indicate an SPL build. This means that SPL_ is
no-longer set.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/freescale/common/Makefile b/board/freescale/common/Makefile
index c491dc8..c2c86c0 100644
--- a/board/freescale/common/Makefile
+++ b/board/freescale/common/Makefile
@@ -34,7 +34,7 @@
 endif
 obj-$(I2C_COMMON)		+= i2c_common.o
 obj-$(CONFIG_FSL_USE_PCA9547_MUX)		+= i2c_mux.o
-obj-$(CONFIG_$(SPL_)VID)	+= vid.o
+obj-$(CONFIG_$(XPL_)VID)	+= vid.o
 obj-$(CONFIG_FSL_QIXIS)	+= qixis.o
 ifndef CONFIG_XPL_BUILD
 obj-$(CONFIG_ID_EEPROM)	+= sys_eeprom.o
@@ -54,7 +54,7 @@
 obj-$(CONFIG_TARGET_P3041DS)		+= ics307_clk.o
 obj-$(CONFIG_TARGET_P4080DS)		+= ics307_clk.o
 obj-$(CONFIG_TARGET_P5040DS)		+= ics307_clk.o
-ifeq ($(CONFIG_$(SPL_)POWER_LEGACY),y)
+ifeq ($(CONFIG_$(XPL_)POWER_LEGACY),y)
 obj-$(CONFIG_POWER_PFUZE100)	+= pfuze.o
 endif
 obj-$(CONFIG_DM_PMIC_PFUZE100)	+= pfuze.o