ALSA: usb-audio: Add sanity checks in v2 clock parsers

commit 0a62d6c966956d77397c32836a5bbfe3af786fc1 upstream.

The helper functions to parse and look for the clock source, selector
and multiplier unit may return the descriptor with a too short length
than required, while there is no sanity check in the caller side.
Add some sanity checks in the parsers, at least, to guarantee the
given descriptor size, for avoiding the potential crashes.

Fixes: 79f920fb ("ALSA: usb-audio: parse clock topology of UAC2 devices")
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>