V4L/DVB (6323): V4L: cinergyT2, remove bad usage of ERESTARTSYS

cinergyT2, remove bad usage of ERESTARTSYS

test of cinergyt2->disconnect_pending doesn't ensure pending signal and so
ERESTARTSYS would reach userspace, which is not permitted. Change it to
EAGAIN.

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>