ALSA: usb-audio: Fix EP matching for continuous rates

The function to evaluate the match of the parameters with an EP
assumes only the discrete rate tables and doesn't handle the
continuous rates properly.

This patch fixes match_endpoint_audioformats() to handle the
continuous rates.  Also the almost useless debug prints there are
dropped.

Tested-by: Keith Milner <kamilner@superlative.org>
Tested-by: Dylan Robinson <dylan_robinson@motu.com>
Link: https://lore.kernel.org/r/20201123085347.19667-25-tiwai@suse.de


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