PCI: designware: add host_init error handling

This patch add support to return value from host_init() callback from drivers,
so that the designware libary can handle or pass it to proper place. Issue with
void return type is that errors or error handling within host_init() callback
are never know to designware code, which could go ahead and access registers
even in error cases.

Typical case in qcom controller driver is to turn off clks in case of errors,
if designware code continues to read/write register when clocks are turned off
the board would reboot/lockup.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>