qup_i2c: export qup_i2c_init_driver

Drivers like onsemi-ncp6335d and fan53555 are clients of i2c-qup driver.
In some targets, these clients have to initialize and probe early before
the i2c-qup driver is ready. Hence export qup_i2c_init_driver to make sure
i2c-qup driver is ready when its clients need to probe.

Change-Id: I0f866d1c4239f9c72f6753674c2283e97f3a3691
Signed-off-by: Ke Liu <keliu@codeaurora.org>