USB: ehci-ppc-of: problems in unwind

The iounmap(ehci->ohci_hcctrl_reg); should be the first thing we do
because the ioremap() was the last thing we did.  Also if we hit any of
the goto statements in the original code then it would have led to a
NULL dereference of "ehci".  This bug was introduced in: 796bcae7
"USB: powerpc: Workaround for the PPC440EPX USBH_23 errata [take 3]"

I modified the few lines in front a little so that my code didn't
obscure the return success code path.

Signed-off-by: Dan Carpenter <error27@gmail.com>
Reviewed-by: Grant Likely <grant.likely@secretlab.ca>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>