tools headers: Update x86's syscall_64.tbl and uapi/asm-generic/unistd

To pick up the changes introduced in the following csets:

  2b188cc1 ("Add io_uring IO interface")
  edafccee ("io_uring: add support for pre-mapped user IO buffers")
  3eb39f47 ("signal: add pidfd_send_signal() syscall")

This makes 'perf trace' to become aware of these new syscalls, so that
one can use them like 'perf trace -e ui_uring*,*signal' to do a system
wide strace-like session looking at those syscalls, for instance.

For example:

  # perf trace -s io_uring-cp ~acme/isos/RHEL-x86_64-dvd1.iso ~/bla

   Summary of events:

   io_uring-cp (383), 1208866 events, 100.0%

     syscall         calls   total    min     avg     max   stddev
                             (msec) (msec)  (msec)  (msec)     (%)
     -------------- ------ -------- ------ ------- -------  ------
     io_uring_enter 605780 2955.615  0.000   0.005  33.804   1.94%
     openat              4  459.446  0.004 114.861 459.435 100.00%
     munmap      ...