Fix the following warning:

  igt_fb.c: In function 'igt_create_fb_with_bo_size':
  igt_fb.c:414:2: warning: format '%llx' expects argument of type
    'long long unsigned int', but argument 9 has type 'uint64_t' [-Wformat=]

  igt_debug("%s(width=%d, height=%d, format=0x%x [bpp=%d], tiling=%llx, size=%d\n",

introduced by commit:

  commit e36091d1


  Author: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
  Date:   Tue Mar 3 14:11:01 2015 +0000

      tiling: Convert framebuffer helpers to use fb modifiers

Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>