ARM: OMAP1: OHCI: use platform_data fn ptr to enable OCPI bus

The OMAP1 OHCI driver needs to enable the OCPI IP block before it can
work.  Previously, the driver was simply calling a symbol defined in
the OMAP platform code, but this is incorrect: drivers should be fully
decoupled from platform and architecture code.

So instead, modify the driver to call through a platform_data function
pointer instead.  We skip any DT aspect, since OMAP1 is not scheduled
to be converted to DT in the near future.

This resolves the following sparse warning:

It also gets rid of a cpu_is_omap16xx() call in a driver.

In the long term, it probably makes sense to move the OCPI bus code to
somewhere under drivers/.  This should avoid the whole platform_data/DT
issue with this function.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Felipe Balbi <balbi@ti.com>
Cc: Anand Gadiyar <gadiyar@ti.com>
Acked-by: Felipe Balbi <balbi@ti.com>