ARM: omap3: Set SPL stack size to 8KB, image to 54KB.

With older toolchains it is possible to not fit entirely into the 45KB
that we had assigned to SPL.  Adjust to allow for 8KB of stack (which
should be more than required) and 54KB of text/data.

Cc: Vaibhav Hiremath <hvaibhav@ti.com>
Cc: Nagendra T S <nagendra@mistralsolutions.com>
Cc: Thomas Weber <weber@corscience.de>
Cc: Ilya Yanok <yanok@emcraft.com>
Cc: Steve Sakoman <sakoman@gmail.com>
Cc: Stefano Babic <sbabic@denx.de>
Signed-off-by: Tom Rini <trini@ti.com>
Acked-by: Stefano Babic <sbabic@denx.de>
Acked-by: Vaibhav Hiremath <hvaibhav@ti.com>