openrisc: Fix broken paths to arch/or32

OpenRISC was mainlined as "openrisc", not "or32".
vmlinux.lds is generated from vmlinux.lds.S.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Stafford Horne <shorne@gmail.com>