ARM: OMAP: Clean-up omap1 low-level io init and ensure cache & tlb flushing

Caches and tlb must be flushed after map_io as pointed out by RMK on
linux-arm-kernel mailing list.

This patch adds does following:

- Move hw init from omap_map_common_io() to new function omap1_init_common_hw()

- Ensure cache and tlb flushing is done in omap_map_common_io() because of
  cpu detection

- Ensure cache and tlb flushing is done after mapping sram

- Remove old unused init check code