arm: bootm: Disable LMB reservation for command line and board info on arm64

On arm64, board info is not applicable and kernel command line patched into
the DT, so the LMB reservation here makes no sense anymore. On legacy arm32,
this might still be necessary on systems which do not use DT or use legacy
ATAGS. Disable this LMB reservation on arm64.

This also permits Linux DT to specify reserved memory node at address close
to the end of DRAM bank, i.e. overlaping with U-Boot location. Since after
boot, U-Boot will be no more, this is OK.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Cc: Hai Pham <hai.pham.ud@renesas.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Cc: Stephen Warren <swarren@nvidia.com>
Cc: Tom Rini <trini@konsulko.com>