ALSA: line6: remove line6_set_raw declaration

line6_set_raw has been removed since
commit 9f673d7a ("staging: line6: drop CONFIG_LINE6_USB_RAW"),
so remove it.
Signed-off-by: Gaosheng Cui <cuigaosheng1@huawei.com>
Link: https://lore.kernel.org/r/20220909035443.1065737-2-cuigaosheng1@huawei.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/usb/line6/driver.h

@@ -193,8 +193,6 @@ extern int line6_send_raw_message_async(struct usb_line6 *line6,
 					const char *buffer, int size);
 extern int line6_send_sysex_message(struct usb_line6 *line6,
 				    const char *buffer, int size);
-extern ssize_t line6_set_raw(struct device *dev, struct device_attribute *attr,
-			     const char *buf, size_t count);
 extern int line6_version_request_async(struct usb_line6 *line6);
 extern int line6_write_data(struct usb_line6 *line6, unsigned address,
 			    void *data, unsigned datalen);