ARM: vf610: Add SoC and CPU type detection

Vybrid product family consists of several rather similar SoC which
can be determined by softare during boot time. This allows use of
variable ${soc} for Linux device tree files. Detect VF5xx CPU's by
reading the CPU count register. We can determine the second number
of the CPU type (VF6x0) which indicates the presence of a L2 cache.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Sanchayan Maity <maitysanchayan@gmail.com>