OMAP: control: move plat-omap/control.h to mach-omap2/control.h

Only OMAP2+ platforms have the System Control Module (SCM) IP block.
In the past, we've kept the SCM header file in plat-omap.  This has
led to abuse - device drivers including it; includes being added that
create implicit dependencies on OMAP2+ builds; etc.

In response, move the SCM headers into mach-omap2/.

As part of this, remove the direct SCM access from the OMAP UDC
driver.  It was clearly broken.  The UDC code needs an indepth review for
use on OMAP2+ chips.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Cory Maccarrone <darkstar6262@gmail.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>