greybus: arche-apb-ctrl: deassert reset at the end of probe

Now the complete handshaking between AP<=>SVC would be
offloaded to parent driver (arche-platform) who is
responsible for SVC control, so the apb-ctrl driver can
just simply bring APB's out of reset during probe itself.

Along with deasserting reset, this patch renames the local fn
to exclusively use it for reset purpose.

Note that, driver is exporting reset gpio to
user, so user can still flash FW from prompt.

Signed-off-by: Vaibhav Hiremath <vaibhav.hiremath@linaro.org>
Tested-by: Michael Scott <michael.scott@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>