ALSA: usb-audio: fix UAC2 control value queries

For RANGE requests, we should only query as much bytes as we're in fact
interested in.

For CUR requests, we shouldn't confuse the firmware with an overlong
request but just ask for 2 bytes.

This might need fixing in the future as it's not entirely clear when to
dispatch 1-byte, 2-byte and 4-byte request blocks. For now, we assume
everything is coded in 16bit - this works for all firmware
implementations I've seen.

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Reported-by: Alex Lee <alexlee188@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>