shader: add missing precision specifier

In GLES, these need a precision specifier, otherwise we get
compile errors.

This fixes a shader-compile error on OpenGL ES 3.1.

Signed-off-by: Erik Faye-Lund <erik.faye-lund@collabora.com>
Reviewed-by: Gurchetan Singh <gurchetansingh@chromium.org>
Signed-off-by: Dave Airlie <airlied@redhat.com>

src/vrend_shader.c

@@ -4126,7 +4126,7 @@ static void *emit_sampler_decl(struct dump_ctx *ctx, char *glsl_hdr, uint32_t i,
 
    /* GLES does not support 1D textures -- we use a 2D texture and set the parameter set to 0.5 */
    if (ctx->cfg->use_gles && texture_type == TGSI_TEXTURE_1D)
-      snprintf(buf, 255, "uniform %csampler2D %ssamp%d;\n", ptc, sname, i);
+      snprintf(buf, 255, "uniform highp %csampler2D %ssamp%d;\n", ptc, sname, i);
    else if (range)
       snprintf(buf, 255, "uniform %s%csampler%s %ssamp%d[%d];\n", precision, ptc, stc, sname, i, range);
    else