selftests/nolibc: drop unnecessary sys/io.h include

selftests/nolibc: drop unnecessary sys/io.h include

The include of sys/io.h is not necessary anymore since
commit 67eb617a8e1e ("selftests/nolibc: simplify call to ioperm").
It's existence is also problematic as the header does not exist on all
architectures.

Reported-by: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Willy Tarreau <w@1wt.eu>
Link: https://lore.kernel.org/r/20250324-nolibc-ioperm-v1-1-8a7cfb2876ae@weissschuh.net