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/drivers/led/Makefile b/drivers/led/Makefile
index e27aa48..aa64a38 100644
--- a/drivers/led/Makefile
+++ b/drivers/led/Makefile
@@ -10,6 +10,6 @@
 obj-$(CONFIG_LED_BCM6753) += led_bcm6753.o
 obj-$(CONFIG_LED_BCM6858) += led_bcm6858.o
 obj-$(CONFIG_LED_PWM) += led_pwm.o
-obj-$(CONFIG_$(SPL_)LED_GPIO) += led_gpio.o
+obj-$(CONFIG_$(XPL_)LED_GPIO) += led_gpio.o
 obj-$(CONFIG_LED_CORTINA) += led_cortina.o
 obj-$(CONFIG_LED_LP5562) += led_lp5562.o