Initial support for Allwinner's Security ID fuses

Allwinner has electric fuses (efuse) on their line of chips. This driver
reads those fuses and exports them as a sysfs node. Also a symbol is exported
for in-kernel useage.

While initially these fuses are used to somewhat determin the chipID, these
appear to be writeable by the user and thus can be used for other purpouses.
For example storing a 128 bit root key, a unique serial number, which could
then even be used as a MAC address.

Because writing to e-fuses can be potentially dangerous, and are certainly
not as often writable (if at all) as flash memory, these shouldn't be easily
changeable, hence only a read-only mode. An offline tool to write the fuses
is in the works.

Currently supported are the following known chips:
Allwinner sun4i (A10)
Allwinner sun5i (A13)

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Add sunxi-sid to dts for sun4i and sun5i

This should add support for the sunxi-sid driver to the device table for sun4i and sun5i

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>
Add the CPU serial as the first 'user' of the Allwinner SID

/proc/cpuinfo exposes a CPU serial number. This patch exports sunxi-sid
to be readable across the kernel, and uses the LSB 64 bits as serial.

It should be noted, that once the user uses SID for other things, this
is no longer relevant, random rather.