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/power/Makefile b/drivers/power/Makefile
index 5a98719..3f4d56f 100644
--- a/drivers/power/Makefile
+++ b/drivers/power/Makefile
@@ -3,8 +3,8 @@
 # Copyright (c) 2009 Wind River Systems, Inc.
 # Tom Rix <Tom.Rix at windriver.com>
 
-obj-$(CONFIG_$(SPL_TPL_)ACPI_PMC) += acpi_pmc/
-obj-$(CONFIG_$(SPL_TPL_)POWER_DOMAIN) += domain/
+obj-$(CONFIG_$(PHASE_)ACPI_PMC) += acpi_pmc/
+obj-$(CONFIG_$(PHASE_)POWER_DOMAIN) += domain/
 obj-y += pmic/
 obj-y += regulator/
 
@@ -23,9 +23,9 @@
 obj-$(CONFIG_TPS6586X_POWER)	+= tps6586x.o
 obj-$(CONFIG_TWL4030_POWER)	+= twl4030.o
 obj-$(CONFIG_PALMAS_POWER)	+= palmas.o
-obj-$(CONFIG_$(SPL_TPL_)POWER_LEGACY) += power_core.o
+obj-$(CONFIG_$(PHASE_)POWER_LEGACY) += power_core.o
 obj-$(CONFIG_DIALOG_POWER) += power_dialog.o
 obj-$(CONFIG_POWER_FSL) += power_fsl.o
-obj-$(CONFIG_$(SPL_TPL_)POWER_I2C) += power_i2c.o
+obj-$(CONFIG_$(PHASE_)POWER_I2C) += power_i2c.o
 obj-$(CONFIG_POWER_SPI) += power_spi.o
 obj-$(CONFIG_POWER_MT6323) += mt6323.o