common: memtop: add logic to detect ram_top

common: memtop: add logic to detect ram_top

Add generic logic to determine the ram_top value for boards. Earlier,
this was achieved in an indirect manner through a set of LMB API's.
That has since changed so that the LMB code is available only after
relocation. Replace those LMB calls with a single call to
get_mem_top() to determine the value of ram_top.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Link: https://lore.kernel.org/r/20241025172724.195093-2-sughosh.ganu@linaro.org
Signed-off-by: Michal Simek <michal.simek@amd.com>