x86: Move install_e820_map() out of zimage.c

install_e820_map() has nothing to do with zimage related codes.
Move it to a dedicated place.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/Makefile b/arch/x86/lib/Makefile
index 6ecd6db..169062e 100644
--- a/arch/x86/lib/Makefile
+++ b/arch/x86/lib/Makefile
@@ -12,6 +12,7 @@
 obj-y	+= cmd_boot.o
 obj-$(CONFIG_HAVE_FSP) += cmd_hob.o
 obj-$(CONFIG_EFI) += efi/
+obj-y	+= e820.o
 obj-y	+= gcc.o
 obj-y	+= init_helpers.o
 obj-y	+= interrupts.o