i2c: xiic: Fix pm_runtime_set_suspended() with runtime pm enabled

It is not valid to call pm_runtime_set_suspended() for devices
with runtime PM enabled because it returns -EAGAIN if it is enabled
already and working. So, call pm_runtime_disable() before to fix it.

Fixes: 36ecbcab ("i2c: xiic: Implement power management")
Cc: <stable@vger.kernel.org> # v4.6+
Signed-off-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>