ARM: DRA752: add detection of SoC information

Currently the files in /sys/devices/soc0/ show no information about
DRA7. Few userspace programs do depend on this information to make SoC
specific support. So update logic to detect the relevant information and
provide to userspace.

Signed-off-by: Nishanth Menon <nm@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>