tgsi: fixes error: ‘enum pipe_shader_type’ declared in tgsi_info.h

tgsi: fixes error: ‘enum pipe_shader_type’ declared  in tgsi_info.h

error message:
../../src/gallium/auxiliary/tgsi/tgsi_info.h:92:30: error: ‘enum pipe_shader_type’ declared inside parameter list will not be visible outside of this definition or declaration [-Werror]
   92 | tgsi_get_processor_name(enum pipe_shader_type processor);

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19676>