drm/zte: remove unneeded semicolon

Fix the following coccicheck warning:

drivers/gpu/drm/zte/zx_vga.c:158:2-3: Unneeded semicolon
drivers/gpu/drm/zte/zx_vga.c:171:2-3: Unneeded semicolon
drivers/gpu/drm/zte/zx_vga.c:179:2-3: Unneeded semicolon

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Acked-by: Shawn Guo <shawnguo@kernel.org>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200504113230.40588-1-yanaijie@huawei.com