common: memtop: Fix the return type for find_ram_top

common: memtop: Fix the return type for find_ram_top

As the return type is "int" for find_ram_top() function and
returning the "base" which is of phys_addr_t is breaking when the
"base" address is 64-bit. So fix this by updating the return type as
phys_addr_t.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Reviewed-by: Michal Simek <michal.simek@amd.com>
Acked-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Link: https://lore.kernel.org/r/20241220030742.1745984-1-venkatesh.abbarapu@amd.com
Signed-off-by: Michal Simek <michal.simek@amd.com>