This API will get the advertised memory size from the bootloader parameter
passed to the kernel. The advertised memory size might be different from
the MemTotal value in /proc/meminfo. This could be due the original design
manufacturer (ODM) reserved part of the memory for the Trusted Execution
Environment.
Test: Run test caes
Bug: 231718727
Change-Id: I06494cb9013048d73a83f2180a9241c2259d46eb