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/arch/x86/cpu/Makefile b/arch/x86/cpu/Makefile
index c21d6d6..8899830 100644
--- a/arch/x86/cpu/Makefile
+++ b/arch/x86/cpu/Makefile
@@ -6,7 +6,7 @@
 # (C) Copyright 2002
 # Daniel Engström, Omicron Ceti AB, daniel@omicron.se.
 
-ifeq ($(CONFIG_$(SPL_)X86_64),y)
+ifeq ($(CONFIG_$(XPL_)X86_64),y)
 extra-y	= start64.o
 else
 ifeq ($(CONFIG_$(SPL_TPL_)X86_16BIT_INIT),y)
@@ -31,7 +31,7 @@
 obj-y	+= cpu_x86.o
 endif
 
-ifndef CONFIG_$(SPL_)X86_64
+ifndef CONFIG_$(XPL_)X86_64
 AFLAGS_REMOVE_call32.o := -mregparm=3 \
 	$(if $(CONFIG_EFI_STUB_64BIT),-march=i386 -m32)
 AFLAGS_call32.o := -fpic -fshort-wchar \
@@ -59,18 +59,18 @@
 ifndef CONFIG_SYS_COREBOOT
 obj-$(CONFIG_$(SPL_TPL_)X86_32BIT_INIT) += irq.o
 endif
-ifndef CONFIG_$(SPL_)X86_64
-obj-$(CONFIG_$(SPL_)SMP) += mp_init.o
+ifndef CONFIG_$(XPL_)X86_64
+obj-$(CONFIG_$(XPL_)SMP) += mp_init.o
 endif
 obj-y += mtrr.o
 obj-$(CONFIG_PCI) += pci.o
-ifndef CONFIG_$(SPL_)X86_64
+ifndef CONFIG_$(XPL_)X86_64
 obj-$(CONFIG_SMP) += sipi_vector.o
 endif
 obj-y += turbo.o
 obj-$(CONFIG_HAVE_ACPI_RESUME) += wakeup.o
 
-ifeq ($(CONFIG_$(SPL_)X86_64),y)
+ifeq ($(CONFIG_$(XPL_)X86_64),y)
 obj-y += x86_64/
 else
 obj-y += i386/