app: aboot: select usb controller to be used at runtime

Instead of compile time selection, query the target at runtime
to select the usb controller to be used for fastboot.

Change-Id: Ib0081b0813589781b96b8993358223db196d1dbb
diff --git a/app/aboot/fastboot.h b/app/aboot/fastboot.h
index 0703402..11355da 100644
--- a/app/aboot/fastboot.h
+++ b/app/aboot/fastboot.h
@@ -11,7 +11,7 @@
  *    notice, this list of conditions and the following disclaimer.
  *  * Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in
- *    the documentation and/or other materials provided with the 
+ *    the documentation and/or other materials provided with the
  *    distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
@@ -21,7 +21,7 @@
  * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
@@ -35,8 +35,9 @@
 #define MAX_GET_VAR_NAME_SIZE   256
 
 int fastboot_init(void *xfer_buffer, unsigned max);
+void fastboot_stop(void);
 
-/* register a command handler 
+/* register a command handler
  * - command handlers will be called if their prefix matches
  * - they are expected to call fastboot_okay() or fastboot_fail()
  *   to indicate success/failure before returning