ARM: OMAP4+: Remove static iotable mappings for SRAM

In order to handle errata I688, a page of sram was reserved by doing a
static iotable map. Now that we use gen_pool to manage sram, we can
completely remove all of these static mappings and use gen_pool_alloc()
to get the one page of sram space needed to implement errata I688.
omap_bus_sync will be NOP until SRAM initialization happens.

Suggested-by: Sekhar Nori <nsekhar@ti.com>
Signed-off-by: Rajendra Nayak <rnayak@ti.com>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>