ALSA: usb-audio: Set 48 kHz rate for Rodecaster

Like the Line6 devices, the Rode Rodecaster Pro does not support
UAC2_CS_RANGE and only supports a sample rate of 48 kHz.

Tested against a Rode Rodecaster Pro.

Tested-by: Christopher Swenson <swenson@swenson.io>
Signed-off-by: Christopher Swenson <swenson@swenson.io>
Cc: <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/ebdb9e72-9649-0b5e-b9b9-d757dbf26927@swenson.io
Signed-off-by: Takashi Iwai <tiwai@suse.de>