ARM: OMAP4: Move TEXT_BASE down to non-HS limit

With the current scenario SPL size is being overlapped with the public
stack and not allowing any OMAP4 device to boot. So the suggestion came
up was to move the TEXT_BASE down to non-HS limit. Fixing the same and
also moving the SRAM_SCRATCH_SPACE_ADDR up to the end of image
downloadable area.
Discussion on this can be seen here:
https://www.mail-archive.com/u-boot@lists.denx.de/msg127147.html



Tested on OMAP4460 PANDA.

Reported-by: Chao Xu <caesarxuchao@gmail.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@ti.com>