This adds the appropriate device-tree compatible and quirk data for
hooking frontend support for the A20. It supports the FIR coefficients
ready bit but not the access control bit. It also takes different phase
values than the A33 for these coefficients.

The compatible is already used in the A10 device-tree and already
documented in the device-tree bindings.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190118145133.21281-23-paul.kocialkowski@bootlin.com