ARM: davinci: sram: switch from iotable to ioremapped regions

The current davinci init sets up SRAM in iotables. There has been
an observed failure to boot a da850 with 128K specified in the
iotable.

Make the davinci sram allocator do an ioremap of the region
specified by the entries in davinci_soc_info before registering
with gen_pool_add_virt(). Remove all iotable SRAM mappings and
SRAM_VIRT.

Regression tested suspend/resume on AM180x EVM.

Signed-off-by: Ben Gardiner <bengardiner@nanometrics.ca>
Signed-off-by: Matt Porter <mporter@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>