usb: chipidea: host: more enhancement when ci->hcd is NULL

Like http://marc.info/?l=linux-usb&m=138200449428874&w=2

 said:
two more things are needed to be done:

- If host_start fails, the host_stop should not be called, so we
add check that ci->hcd is not NULL.
- if the host_start fails at the beginning, we need to consider
regulator mismatch issue.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>