drm/panel: make sharp_ls055d1sx04 static

This symbol is not used outside of panel-novatek-nt35950.c, so marks it
static.

Fixes the following sparse warning:

drivers/gpu/drm/panel/panel-novatek-nt35950.c:671:33: warning: symbol
'sharp_ls055d1sx04' was not declared. Should it be static?

Reported-by: Abaci Robot <abaci@linux.alibaba.com>
Fixes: 623a3531 ("drm/panel: Add driver for Novatek NT35950 DSI DriverIC panels")
Signed-off-by: chongjiapeng <jiapeng.chong@linux.alibaba.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/1634640029-12335-1-git-send-email-jiapeng.chong@linux.alibaba.com