[x86] remove uses of magic macros for boot_params access

Instead of using magic macros for boot_params access, simply use the
boot_params structure.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/boot/Makefile

diff --git a/arch/x86/boot/Makefile b/arch/x86/boot/Makefile
index e8756e5..89dbf97 100644
--- a/arch/x86/boot/Makefile
+++ b/arch/x86/boot/Makefile
@@ -39,6 +39,7 @@
 setup-y		+= video-vga.o
 setup-y		+= video-vesa.o
 setup-y		+= video-bios.o
+
 targets		+= $(setup-y)
 hostprogs-y	:= tools/build