nios2: put setup.h in uapi

This header file is exported, but from a userland pov, it's just a wrapper
to asm-generic/setup.h.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Reviewed-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>

arch/nios2/include/uapi/asm/Kbuild

@@ -2,4 +2,5 @@ include include/uapi/asm-generic/Kbuild.asm
 
 header-y += elf.h
 
+generic-y += setup.h
 generic-y += ucontext.h