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/env/Makefile b/env/Makefile
index c5145c1..a54e924 100644
--- a/env/Makefile
+++ b/env/Makefile
@@ -3,10 +3,10 @@
 # (C) Copyright 2004-2006
 # Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 
-obj-$(CONFIG_$(SPL_TPL_)ENV_SUPPORT) += common.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_SUPPORT) += env.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_SUPPORT) += attr.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_SUPPORT) += flags.o
+obj-$(CONFIG_$(PHASE_)ENV_SUPPORT) += common.o
+obj-$(CONFIG_$(PHASE_)ENV_SUPPORT) += env.o
+obj-$(CONFIG_$(PHASE_)ENV_SUPPORT) += attr.o
+obj-$(CONFIG_$(PHASE_)ENV_SUPPORT) += flags.o
 
 ifndef CONFIG_XPL_BUILD
 obj-y += callback.o
@@ -20,12 +20,12 @@
 obj-$(CONFIG_ENV_IS_IN_UBI) += ubi.o
 endif
 
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_NOWHERE) += nowhere.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_IN_MMC) += mmc.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_IN_FAT) += fat.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_IN_EXT4) += ext4.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_IN_NAND) += nand.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_IN_SPI_FLASH) += sf.o
-obj-$(CONFIG_$(SPL_TPL_)ENV_IS_IN_FLASH) += flash.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_NOWHERE) += nowhere.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_IN_MMC) += mmc.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_IN_FAT) += fat.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_IN_EXT4) += ext4.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_IN_NAND) += nand.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_IN_SPI_FLASH) += sf.o
+obj-$(CONFIG_$(PHASE_)ENV_IS_IN_FLASH) += flash.o
 
 CFLAGS_embedded.o := -Wa,--no-warn -DENV_CRC=$(shell tools/envcrc 2>/dev/null)