x86: Add implementations of setjmp() and longjmp()

Bring in these functions from Linux v4.4. They will be needed for EFI loader
support.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/x86/cpu/Makefile b/arch/x86/cpu/Makefile
index 2667e0b..f5b8c9e 100644
--- a/arch/x86/cpu/Makefile
+++ b/arch/x86/cpu/Makefile
@@ -10,7 +10,7 @@
 
 extra-y	= start.o
 obj-$(CONFIG_X86_RESET_VECTOR) += resetvec.o start16.o
-obj-y	+= interrupts.o cpu.o cpu_x86.o call64.o
+obj-y	+= interrupts.o cpu.o cpu_x86.o call64.o setjmp.o
 
 AFLAGS_REMOVE_call32.o := -mregparm=3 \
 	$(if $(CONFIG_EFI_STUB_64BIT),-march=i386 -m32)