ARM: OMAP1: Fix randconfig builds if ARCH_OMAP15XX not selected

With the omap1 SPARSE_IRQ changes mach/irqs.h is no longer
automatically included. Turns out now we rely on ARCH_OMAP15XX
including hardware.h from memory.h, so without ARCH_OMAP15XX
we get build failures.

As we have legacy drivers still relying on these indirect
includes, let's not add more mach includes to the drivers.
Those have to be removed anyways for multiplatform support.

Let's fix up mach-omap1 to include soc.h where cpu_is_omap
checks are done, and common.h for board-*.c files.

But let's keep the indirect memory.h include for now to avoid
unnecessary churn in the drivers.

Signed-off-by: Tony Lindgren <tony@atomide.com>