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/timer/Makefile b/drivers/timer/Makefile
index fec4af3..7a847e8 100644
--- a/drivers/timer/Makefile
+++ b/drivers/timer/Makefile
@@ -5,14 +5,14 @@
 obj-y += timer-uclass.o
 obj-$(CONFIG_ADI_SC5XX_TIMER) += adi_sc5xx_timer.o
 obj-$(CONFIG_ALTERA_TIMER)	+= altera_timer.o
-obj-$(CONFIG_$(SPL_)ANDES_PLMT_TIMER) += andes_plmt_timer.o
+obj-$(CONFIG_$(XPL_)ANDES_PLMT_TIMER) += andes_plmt_timer.o
 obj-$(CONFIG_ARC_TIMER)	+= arc_timer.o
 obj-$(CONFIG_ARM_TWD_TIMER)	+= arm_twd_timer.o
 obj-$(CONFIG_AST_TIMER)	+= ast_timer.o
 obj-$(CONFIG_AST_IBEX_TIMER)	+= ast_ibex_timer.o
 obj-$(CONFIG_ATCPIT100_TIMER) += atcpit100_timer.o
-obj-$(CONFIG_$(SPL_)ATMEL_PIT_TIMER) += atmel_pit_timer.o
-obj-$(CONFIG_$(SPL_)ATMEL_TCB_TIMER) += atmel_tcb_timer.o
+obj-$(CONFIG_$(XPL_)ATMEL_PIT_TIMER) += atmel_pit_timer.o
+obj-$(CONFIG_$(XPL_)ATMEL_TCB_TIMER) += atmel_tcb_timer.o
 obj-$(CONFIG_CADENCE_TTC_TIMER)	+= cadence-ttc.o
 obj-$(CONFIG_DESIGNWARE_APB_TIMER)	+= dw-apb-timer.o
 obj-$(CONFIG_FTTMR010_TIMER)	+= fttmr010_timer.o
@@ -27,7 +27,7 @@
 obj-$(CONFIG_ROCKCHIP_TIMER) += rockchip_timer.o
 obj-$(CONFIG_SANDBOX_TIMER)	+= sandbox_timer.o
 obj-$(CONFIG_SP804_TIMER)	+= sp804_timer.o
-obj-$(CONFIG_$(SPL_)RISCV_ACLINT) += riscv_aclint_timer.o
+obj-$(CONFIG_$(XPL_)RISCV_ACLINT) += riscv_aclint_timer.o
 obj-$(CONFIG_ARM_GLOBAL_TIMER)	+= arm_global_timer.o
 obj-$(CONFIG_STM32_TIMER)	+= stm32_timer.o
 obj-$(CONFIG_TEGRA_TIMER)	+= tegra-timer.o