mesa/main: fix regression in extension-checking

This condition accidentally got inverted when cleaning up code, whoops.

Fixes: 3251f321b8 ("mesa: some cleanups for texparam extension checks")
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/34248>

src/mesa/main/texparam.c

@@ -2762,7 +2762,7 @@ get_tex_parameteriv(struct gl_context *ctx,
          break;
 
       case GL_TEXTURE_CUBE_MAP_SEAMLESS:
-         if (_mesa_has_AMD_seamless_cubemap_per_texture(ctx))
+         if (!_mesa_has_AMD_seamless_cubemap_per_texture(ctx))
             goto invalid_pname;
          *params = (GLint) obj->Sampler.Attrib.CubeMapSeamless;
          break;