arm64: use common of_flat_dt_get_machine_name

Convert arm64 to use the common of_flat_dt_get_machine_name function.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Git-commit: f2b99bccae87de82a5d03838abe85d604ee7e525
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Ian Maund <imaund@codeaurora.org>