tools/testing/selftests/sigaltstack/sas.c: improve output of sigaltstack testcase

tools/testing/selftests/sigaltstack/sas.c: improve output of sigaltstack testcase

Currently it uses %i for bitmasks, which makes it difficult to properly
decode the values.  Use %x instead.

Link: http://lkml.kernel.org/r/b7b4c45d-2f21-de6c-d1c8-16c8386da27c@list.ru
Signed-off-by: Stas Sergeev <stsp@users.sourceforge.net>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>