global: Rename SPL_TPL_ to PHASE_

Use PHASE_ as the symbol to select a particular XPL build. This means
that SPL_TPL_ is no-longer set.

Update the comment in bootstage to refer to this symbol, instead of
SPL_

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/sysreset/Makefile b/drivers/sysreset/Makefile
index a6a0584..796fc9e 100644
--- a/drivers/sysreset/Makefile
+++ b/drivers/sysreset/Makefile
@@ -2,7 +2,7 @@
 #
 # (C) Copyright 2016 Cadence Design Systems Inc.
 
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET) += sysreset-uclass.o
+obj-$(CONFIG_$(PHASE_)SYSRESET) += sysreset-uclass.o
 obj-$(CONFIG_ARCH_ASPEED) += sysreset_ast.o
 obj-$(CONFIG_ARCH_ROCKCHIP) += sysreset_rockchip.o
 obj-$(CONFIG_ARCH_STI) += sysreset_sti.o
@@ -10,24 +10,24 @@
 obj-$(CONFIG_SYSRESET_CV1800B) += sysreset_cv1800b.o
 obj-$(CONFIG_POWEROFF_GPIO) += poweroff_gpio.o
 obj-$(CONFIG_SYSRESET_GPIO) += sysreset_gpio.o
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET_MAX77663) += sysreset_max77663.o
+obj-$(CONFIG_$(PHASE_)SYSRESET_MAX77663) += sysreset_max77663.o
 obj-$(CONFIG_SYSRESET_MPC83XX) += sysreset_mpc83xx.o
 obj-$(CONFIG_SYSRESET_MICROBLAZE) += sysreset_microblaze.o
 obj-$(CONFIG_SYSRESET_OCTEON) += sysreset_octeon.o
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET_PALMAS) += sysreset_palmas.o
+obj-$(CONFIG_$(PHASE_)SYSRESET_PALMAS) += sysreset_palmas.o
 obj-$(CONFIG_SYSRESET_PSCI) += sysreset_psci.o
 obj-$(CONFIG_SYSRESET_SBI) += sysreset_sbi.o
 obj-$(CONFIG_SYSRESET_SOCFPGA) += sysreset_socfpga.o
 obj-$(CONFIG_SYSRESET_SOCFPGA_SOC64) += sysreset_socfpga_soc64.o
 obj-$(CONFIG_SYSRESET_TEGRA) += sysreset_tegra.o
 obj-$(CONFIG_SYSRESET_TI_SCI) += sysreset-ti-sci.o
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET_TPS65910) += sysreset_tps65910.o
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET_TPS80031) += sysreset_tps80031.o
+obj-$(CONFIG_$(PHASE_)SYSRESET_TPS65910) += sysreset_tps65910.o
+obj-$(CONFIG_$(PHASE_)SYSRESET_TPS80031) += sysreset_tps80031.o
 obj-$(CONFIG_SYSRESET_SYSCON) += sysreset_syscon.o
 obj-$(CONFIG_SYSRESET_WATCHDOG) += sysreset_watchdog.o
 obj-$(CONFIG_SYSRESET_RESETCTL) += sysreset_resetctl.o
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET_AT91) += sysreset_at91.o
-obj-$(CONFIG_$(SPL_TPL_)SYSRESET_X86) += sysreset_x86.o
+obj-$(CONFIG_$(PHASE_)SYSRESET_AT91) += sysreset_at91.o
+obj-$(CONFIG_$(PHASE_)SYSRESET_X86) += sysreset_x86.o
 obj-$(CONFIG_SYSRESET_RAA215300) += sysreset_raa215300.o
 obj-$(CONFIG_SYSRESET_QCOM_PSHOLD) += sysreset_qcom-pshold.o
 obj-$(CONFIG_TARGET_XTFPGA) += sysreset_xtfpga.o