ac/rgp: Fix single-bit-bitfield-constant-conversion warning

ac/rgp: Fix single-bit-bitfield-constant-conversion warning

../src/amd/common/ac_rgp.c:119:48: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion]
  119 |    header->flags.is_semaphore_queue_timing_etw = 1;
      |                                                ^ ~

Fixes: ed0c8522437 ("radv: add initial SQTT files generation support")
Signed-off-by: Vinson Lee <vlee@freedesktop.org>
Reviewed-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26839>
(cherry picked from commit 568f61787a5cd1a69c799d935c364138ff415a1e)