drm/vc4: fix argument ordering in vc4_crtc_get_margins()

Cppcheck complains that the declaration doesn't match the function
definition.  Obviously "left" should come before "right".  The caller
and the function implementation are done this way, it's just the
declaration which is wrong so this doesn't affect runtime.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/YH/720FD978TPhHp@mwanda