[ALSA] Fix compile errors with older gcc

Fixed compile errors with older gcc for initialization of a union.
sound/pci/ca0106/ca0106_mixer.c: At top level:
sound/pci/ca0106/ca0106_mixer.c:499: unknown field 'p' specified in initializer
sound/pci/ca0106/ca0106_mixer.c:499: warning: missing braces around initializer
sound/pci/ca0106/ca0106_mixer.c:499: warning: (near initialization for 'snd_ca0106_volume_ctls[0].tlv')

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>