arm: cpu: read all address cells in dt for cpuid

For v8/arm64 platforms the number of address-cells can be 2.
If the same device tree is used on 32-bit platforms,it is
currently reading only one cell of 32-bits.

Fix this by reading both cells for getting the hwid.

Change-Id: Id281b6b8ac3c9312848c39e11019284f970caced
Signed-off-by: Srinivas Ramana <sramana@codeaurora.org>