usb: musb: blackfin: fix typo in platform driver name

The modularization of the Blackfin driver set the name to "musb-blackfin"
in all the boards, but "musb-bfin" in the driver itself.  Since the driver
file name uses "blackfin", change the driver to "musb-blackfin".  This is
also easier as it's only one file to change.

Cc: stable@kernel.org
Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>