fix the SND_FM801_TEA575X dependencies

CONFIG_SND_FM801=y, CONFIG_SND_FM801_TEA575X=m resulted in the following
compile error:

<--  snip  -->

...
  LD      vmlinux
sound/built-in.o: In function 'snd_fm801_free':
fm801.c:(.text+0x3c15b): undefined reference to 'snd_tea575x_exit'
sound/built-in.o: In function 'snd_card_fm801_probe':
fm801.c:(.text+0x3cfde): undefined reference to 'snd_tea575x_init'
make: *** [vmlinux] Error 1

<--  snip  -->

This patch fixes kernel Bugzilla #6458.

Signed-off-by: Adrian Bunk <bunk@stusta.de>