V4L/DVB (6795): Add EXPORT_SYMBOL_GPL to the saa7134 video control routines

Those newer functions are used by saa7134-empress. Adds export for them:
+EXPORT_SYMBOL_GPL(saa7134_g_ctrl);
+EXPORT_SYMBOL_GPL(saa7134_s_ctrl);
+EXPORT_SYMBOL_GPL(saa7134_queryctrl);

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>