drm/i915: fix build warning on 32-bit (v2)

/ssd/git/drm-next/drivers/gpu/drm/i915/i915_cmd_parser.c: In function ‘i915_parse_cmds’:
/ssd/git/drm-next/drivers/gpu/drm/i915/i915_cmd_parser.c:405:4: warning: format ‘%ld’ expects argument of type ‘long int’, but argument 5 has type ‘int’ [-Wformat=]
    DRM_DEBUG_DRIVER("CMD: Command length exceeds batch length: 0x%08X length=%d batchlen=%ld\n",
    ^

Signed-off-by: Dave Airlie <airlied@redhat.com>