This patch collapses some one-use functions into their callers.  It also
clones some code for control transfers so we can implement abortable
control transfers with timeout.

This patch is from Alan Stern.

 Remove usb_stor_bulk_msg() and usb_stor_interrupt_msg().  Move their
 functionality into usb_stor_bulk_transfer_buf() and
 usb_stor_intr_transfer().

 Move the functionality of usb_stor_control_msg() into
 usb_stor_ctrl_transfer().

 Remove the unused act_len parameter from usb_stor_intr_transfer().