ALSA: oss - volume control for CSWITCH and CROUTE

Added an else part to check
SNDRV_MIXER_OSS_PRESENT_CVOLUME for MIC (slot 7)
in commit 36c7b833



Similarly, checks and volume control is required for
SNDRV_MIXER_OSS_PRESENT_CSWITCH and SNDRV_MIXER_OSS_PRESENT_CROUTE
as well.

Signed-off-by: Deepika Makhija <deepika.makhija@einfochips.com>
Signed-off-by: Viral Mehta <viral.mehta@einfochips.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>