Fix multiboot compilation

Fix multiboot compilation

Commit dd4239d6574ca41c94fc0d0f77ddc728510ffc57 broke multiboot. It replaced the
instruction "rep insb (%dx), %es:(%edi)" by the binary output of
"addr32 rep insb (%dx), %es:(%di)".

Linuxboot calls the respective helper function in a code16 section. So the
original instruction was automatically translated to its "addr32" equivalent.
For multiboot, we're running in code32 so gcc didn't add the "addr32" which
breaks the instruction.

This patch splits that helper function in one which uses addr32 and one which
does not, so everyone's happy.

The good news is that nobody probably cared so far. The bundled multiboot.bin
binary was built before the change and is thus correct.

Please also put this patch into -stable.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
(cherry picked from commit 590bf491a49670843ee902c47f7ab1de5e9acd06)