[gdb/record] Fix syscall recording some more

I ran into the same gdb.reverse/sigall-reverse.exp failure on ppc64le-linux,
as fixed in commits:
- commit 3686645cec9 ("[gdb/record] Fix return value for svc in
  aarch64_record_branch_except_sys"), and
- commit 4ef576bdb7f ("[gdb/record] Fix return value for syscall in
  loongarch_record_syscall_insn").

The difference with those commits is that the problem is not due to confusion
about a port-local enums (aarch64_record_result, loongarch_record_result).

Instead, the port just treats return values 1 and -1 the same:
...
	  if (tdep->ppc_syscall_record (regcache) != 0)
	    return -1;
...

Fix this by passing through the return value 1 instead.

Likewise on s390x-linux.

Tested on ppc64le-linux and s390x-linux.

Reviewed-by: Abhay Kandpal <abhay@linux.ibm.com>