omap: Split OMAP2_IO_ADDRESS to L3 and L4

This patch splits OMAP2_IO_ADDRESS to OMAP2_L3_IO_ADDRESS and
OMAP2_L4_IO_ADDRESS to reclaim more IO space.

The omap_read*() and omap_write*() functions will work only over
L4 address space. Current omap kernel stack uses these functions
only to access registers over L4 io address space

Note that these macros should only be used when ioremap does
not work. Please use ioremap instead in all new code.

Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>