Kbuild: Always use $(PHASE_)

It is confusing to have both "$(PHASE_)" and "$(XPL_)" be used in our
Makefiles as part of the macros to determine when to do something in our
Makefiles based on what phase of the build we are in. For consistency,
bring this down to a single macro and use "$(PHASE_)" only.

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 43e6a1d..c60a479 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -19,7 +19,7 @@
 obj-$(CONFIG_CMD_BOOTM) += bootm.o
 endif
 obj-y	+= cmd_boot.o
-obj-$(CONFIG_$(XPL_)COREBOOT_SYSINFO)	+= coreboot/
+obj-$(CONFIG_$(PHASE_)COREBOOT_SYSINFO)	+= coreboot/
 obj-$(CONFIG_SEABIOS) += coreboot_table.o
 obj-y	+= early_cmos.o
 obj-y	+= e820.o
@@ -90,7 +90,7 @@
 
 ifdef CONFIG_EFI_STUB
 
-ifeq ($(CONFIG_$(XPL_)X86_64),)
+ifeq ($(CONFIG_$(PHASE_)X86_64),)
 extra-y += $(EFI_CRT0) $(EFI_RELOC)
 endif