USB: Allow compile in g_ether, fix typo

Allows compiling g_ether in and fixes a typo with MUSB_HDRC

Signed-off-by: Tony Lindgren <tony@atomide.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>