V4L/DVB (6384): Replace TDA9887_SET_CONFIG by TUNER_SET_CONFIG

Currently, the only tuner-specific device that allows special
configurations is tda9887. However, tea5767 also may require some
special configurations (for example, to specify a different Xtal freq).

This patch replaces TDA9887_SET_CONFIG by a more generic internal ioctl
(TUNER_SET_CONFIG). The newer one allows specifying what tuner is
appliable to a configuration set, and allows an arbitrary configuration
struct.

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