gl: Don't declare variables in for loop

Fixes compilation error introduced by 43cea54c:

  libweston/gl-renderer.c:2862:2: error: ‘for’ loop initial declarations
  are only allowed in C99 mode
    for (unsigned i = 0; i < ARRAY_LENGTH(swap_damage_ext_to_entrypoint);
    i++) {
    ^

Signed-off-by: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-by: Daniel Stone <daniels@collabora.com>
1 file changed