ARM: OMAP4+: Move SRAM data to DT

Use drivers/misc/sram.c driver to manage SRAM on all DT only
OMAP platforms (am33xx, am43xx, omap4 and omap5) instead of
the existing private plat-omap/sram.c

Address and size related data  is removed from mach-omap2/sram.c
and now passed to drivers/misc/sram.c from DT.

Users can hence use general purpose allocator apis instead of
OMAP private ones to manage and use SRAM.

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>