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>
diff --git a/common/Makefile b/common/Makefile
index 2ee5ef9..3599156 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -7,6 +7,7 @@
 ifndef CONFIG_XPL_BUILD
 obj-y += init/
 obj-y += main.o
+obj-y += memtop.o
 obj-y += exports.o
 obj-y += cli_getch.o cli_simple.o cli_readline.o
 obj-$(CONFIG_HUSH_OLD_PARSER) += cli_hush.o