kernel: Fix arm64 include files

kernel: Fix arm64 include files

This patch fixes the build of gdb and strace on arm64 targets with
kernel 4.19.

Without this patch asm/ptrace.h is including asm/sigcontext.h and this
file defines some structures which are also defined in musl header file
arch/aarch64/bits/signal.h. These two definitions then conflict with
each other and make the build fail.

This was seen locally and also by the build bot. The struct sigcontext,
struct sve_context and some others were defined twice. It looks like
this problem was introduced between 4.14 and 4.19 and it was fixed in
5.0. I already requested to backport this patch to kernel 4.19.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>