drm/msm/mdp5: set varaiable msm8x76_config storage-class-specifier to static

smatch reports
drivers/gpu/drm/msm/disp/mdp5/mdp5_cfg.c:658:26: warning: symbol
  'msm8x76_config' was not declared. Should it be static?

This variable is only used in one file so should be static.

Signed-off-by: Tom Rix <trix@redhat.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Patchwork: https://patchwork.freedesktop.org/patch/530950/
Link: https://lore.kernel.org/r/20230404185329.1925964-1-trix@redhat.com


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>