arm64, numa: Change the numa init functions name to be generic

This is a preparatory patch for unifying numa implementation between
ARM64 & RISC-V. As the numa implementation will be moved to generic
code, rename the arm64 related functions to a generic one.

Signed-off-by: Atish Patra <atish.patra@wdc.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>