gallium+mesa: fix tgsi_semantic array type

Fixes: ed23335a ("gallium: use enums in p_shader_tokens.h (v2)")
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
(cherry picked from commit e7e31b18)