Initial support for Allwinner's Security ID fuses

Allwinner has electric fuses (efuse) on their line of chips. This driver
reads those fuses, seeds the kernel entropy and exports them as a sysfs node.

These fuses are most likly to be programmed at the factory, encoding
things like Chip ID, some sort of serial number etc and appear to be
reasonable unique.
While in theory, these should be writeable by the user, it will probably
be inconvinient to do so. Allwinner recommends that a certain input pin,
labeled 'efuse_vddq', be connected to GND. To write these fuses, 2.5 V
needs to be applied to this pin.

Even so, they can still be used to generate a board-unique mac from, board
unique RSA key and seed the kernel RNG.

Currently supported are the following known chips:
Allwinner sun4i (A10)
Allwinner sun5i (A10s, A13)

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

This patch shall add support for the sunxi-sid driver to the device table for
sun4i and sun5i.

Signed-off-by: Oliver Schinagl <oliver@schinagl.nl>