We can rely on the system kernel and the dump capture kernel themselves in
memory usage.

Being restrictive with 512MB limit may cause kexec tool failure on some
platforms.
Tested-by: NRachel Mozes <rachel.mozes@intel.com>
Reported-by: NRachel Mozes <rachel.mozes@intel.com>
Signed-off-by: NDengcheng Zhu <dzhu@wavecomp.com>
Signed-off-by: NPaul Burton <paul.burton@mips.com>
Patchwork: https://patchwork.linux-mips.org/patch/20568/
Cc: pburton@wavecomp.com
Cc: ralf@linux-mips.org
Cc: linux-mips@linux-mips.org