ALSA: tea575x-tuner: various improvements

Improve tea575x-tuner with various good things from radio-maestro:
- extend frequency range to 50-150MHz
- fix querycap(): card name, CAP_RADIO
- improve g_tuner(): CAP_STEREO, stereo and tuned indication
- improve g_frequency(): tuner index checking and reading frequency from HW
- improve s_frequency(): tuner index and type checking

Signed-off-by: Ondrej Zary <linux@rainbow-software.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>