selftests/bpf: Skip test_bpf_syscall_macro's syscall_arg1 on arm64 and s390

These architectures can provide access to the first syscall argument
only through PT_REGS_PARM1_CORE_SYSCALL().

Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220209021745.2215452-8-iii@linux.ibm.com