usb_cdc: Rename usb_request_bootloader() to bootloader_request()

Rename this board API function to a more generic name.  This is in
preparation for calling the function from the canbus code.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

src/avr/usbserial.c

@@ -7,6 +7,7 @@
 #include <avr/interrupt.h> // USB_COM_vect
 #include <string.h> // NULL
 #include "autoconf.h" // CONFIG_MACH_at90usb1286
+#include "board/misc.h" // bootloader_request
 #include "board/usb_cdc.h" // usb_notify_ep0
 #include "board/usb_cdc_ep.h" // USB_CDC_EP_BULK_IN
 #include "pgm.h" // READP
@@ -179,7 +180,7 @@ usb_set_configure(void)
 }
 
 void
-usb_request_bootloader(void)
+bootloader_request(void)
 {
 }