ARM: omap: Remove stray ARCH_HAS_OPP references

OPP is now a normal kernel library selected by its users rather than a
feature that architectures need to enable so ARCH_HAS_OPP serves no
function any more - remove the selects.

Signed-off-by: Mark Brown <broonie@kernel.org>
Acked-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>