drm/vmwgfx: Fix a size_t/long int format specifier mismatch

On i386 size_t is of course 32bits and using long int throws warnings,
trivially fix it by using the dedicated size_t format.

This is enough to fix the following warning found by the kernel test
robot:
   drivers/gpu/drm/vmwgfx/vmwgfx_gem.c: In function 'vmw_bo_print_info':
>> drivers/gpu/drm/vmwgfx/vmwgfx_gem.c:230:33: warning: format '%ld'
expects argument of type 'long int', but argument 4 has type 'size_t'
{aka 'unsigned int'} [-Wformat=]
     230 |  seq_printf(m, "\t\t0x%08x: %12ld bytes %s, type = %s",
         |                             ~~~~^
         |                                 |
         |                                 long int
         |                             %12d
     231 |      id, bo->base.base.size, placement, type);
         |          ~~~~~~~~~~~~~~~~~~
         |                       |

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Fixes: 8afa13a0 ("drm/vmwgfx: Implement DRIVER_GEM")
Reviewed-by: Martin Krastev <krastevm@vmware.com>
Reviewed-by: Maaz Mombasawala <mombasawalam@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20211215184147.3688785-1-zack@kde.org