ARM: OMAP3+: PRM: add generic API for reconfiguring I/O chain

ARM: OMAP3+: PRM: add generic API for reconfiguring I/O chain

This adds a generic API for reconfiguring the I/O chain. The implementation
will call the SoC specific function registered during init time. The SoC
specific reconfigure functions are also made static, as they don't need
to be accessed outside the PRM driver itself.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Tested-by: Nishanth Menon <nm@ti.com>