bsd-user/elfload.c: Fix set-but-not-used warnings

bsd-user/elfload.c: Fix set-but-not-used warnings

Fix various warnings about set-but-not-used variables on OpenBSD:

bsd-user/elfload.c:1158:15: warning: variable 'mapped_addr' set but not used [-Wunused-but-set-variable]
bsd-user/elfload.c:1165:9: warning: variable 'status' set but not used [-Wunused-but-set-variable]
bsd-user/elfload.c:1168:15: warning: variable 'elf_stack' set but not used [-Wunused-but-set-variable]

Signed-off-by: Peter Maydell <[email protected]>
Reviewed-by: Philippe Mathieu-Daudé <[email protected]>
Message-id: 1500395194[email protected]