PowerPC, add support for recording pipe2 system call.

PowerPC, add support for recording pipe2 system call.

Test gdb.reverse/pipe-reverse.exp fails on Power 10 running the fedora 36
distro.  The gdb record error message is:

  Process record and replay target doesn't support syscall number 317.

System call 317 on PowerPC maps to the pipe2 system call.

This patch adds support for the missing pipe2 system call for PowerPC.

Patch fixes the test failure in gdb.reverse/pipe-reverse.exp.

The patch has been tested on Power 10 with no regression failures.