drm/panel: samsung-s6d7aa0: use pointer for drm_mode in panel desc struct

Fixes compilation issues with older GCC versions and Clang after
changes introduced in commit 6810bb39

 ("drm/panel: Add Samsung
S6D7AA0 panel controller driver"). Tested with GCC 13.1.1, GCC 6.4.0
and Clang 16.0.3.

Fixes the following errors with Clang:

  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:312:14: error: initializer element is not a compile-time constant
          .drm_mode = s6d7aa0_lsl080al02_mode,
                      ^~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:415:14: error: initializer element is not a compile-time constant
          .drm_mode = s6d7aa0_lsl080al03_mode,
                      ^~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:443:14: error: initializer element is not a compile-time constant
          .drm_mode = s6d7aa0_ltl101at01_mode,
                      ^~~~~~~~~~~~~~~~~~~~~~~
  3 errors generated.

Fixes the following errors with GCC:

  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:312:14: error: initializer element is not constant
    .drm_mode = s6d7aa0_lsl080al02_mode,
                ^~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:312:14: note: (near initialization for 's6d7aa0_lsl080al02_desc.drm_mode')
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:415:14: error: initializer element is not constant
    .drm_mode = s6d7aa0_lsl080al03_mode,
                ^~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:415:14: note: (near initialization for 's6d7aa0_lsl080al03_desc.drm_mode')
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:443:14: error: initializer element is not constant
    .drm_mode = s6d7aa0_ltl101at01_mode,
                ^~~~~~~~~~~~~~~~~~~~~~~
  drivers/gpu/drm/panel/panel-samsung-s6d7aa0.c:443:14: note: (near initialization for 's6d7aa0_ltl101at01_desc.drm_mode')

Reported-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/lkml/20230523180212.GA1401867@dev-arch.thelio-3990X
Reported-by: kernelci.org bot <bot@kernelci.org>
Link: https://lore.kernel.org/llvm/646c6def.a70a0220.58c1a.903d@mx.google.com
Fixes: 6810bb39

 ("drm/panel: Add Samsung S6D7AA0 panel controller driver")
Signed-off-by: Artur Weber <aweber.kernel@gmail.com>
Acked-by: Neil Armstrong <neil.armstrong@linaro.org>
Signed-off-by: Neil Armstrong <neil.armstrong@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20230524084324.11840-1-aweber.kernel@gmail.com