ALSA: usb-audio: Fix size validation in convert_chmap_v3()

The "p" pointer is void so sizeof(*p) is 1.  The intent was to check
sizeof(*cs_desc), which is 3, instead.

Fixes: ecfd4116 ("ALSA: usb-audio: Validate UAC3 cluster segment descriptors")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Link: https://patch.msgid.link/aKL5kftC1qGt6lpv@stanley.mountain


Signed-off-by: Takashi Iwai <tiwai@suse.de>