wacom_i2c: Add the latest features

[flying-elephant]

Latest Wacom EMR has new features. Specifically,
those are tilts and height events. The most recent EMR, G14, has a new pen type too.
This patch covers all those functionalities.

[Pinglinux]

Looks good. Thank you!

[Mis012]

@flying-elephant assuming you want to see this merged into mainline Linux at some point, I have the following suggestions:

OF compatible: should be [vendor],XXX, so wacom,XXX; if it was just a driver for hw probably something like wacom,w9002 or whatever the oldest compatible IC is, but since the interface is defined by the fw it may be possible to argue it's a driver for the fw interface rather than any specific chip and therefore something like wacom,emr-i2c makes perfect sense

feature detection/handling: https://github.com/linuxwacom/input-wacom/pull/384/files#diff-516292477f38b98bce2c71946702206bb9ea0d1c46298bc154982dc9d0e817bcR302 should probably check for features->support.distance and features->support.tilt respectively, rather than for the generation (which is deduced from whether the features are supported anyway), and similarly for https://github.com/linuxwacom/input-wacom/pull/384/files#diff-516292477f38b98bce2c71946702206bb9ea0d1c46298bc154982dc9d0e817bcR195
at https://github.com/linuxwacom/input-wacom/pull/384/files#diff-516292477f38b98bce2c71946702206bb9ea0d1c46298bc154982dc9d0e817bcR203 it seems to make sense to differentiate by generation, though idk if it's clear enough what's going on to not warrant a comment

for OF, there should also be a binding (only yaml bindings are supported for new drivers, which are "fun" to write)

I also can't easily find information on what ICs (pens? digitizers? IC fw versions? a combination of these factors?) constitute which generation, it would probably be helpful to add some explanation for that (in the driver or in the binding description, not sure what would be preferred by upstream), e.g

G9: w9002, ...,
G10: ...
G11: ...
G12: ...
...

if it's just a matter of the IC, though I figure it may be more complicated

[flying-elephant]

@Mis012
Thanks, I'll remember how to name OF device.
In order to make the IC information clearer, we may be able to add noticeable comments too.
I'll keep them in mind.

[Mis012]

actually, I believe Samsung uses these ICs with their own incompatible fw interface, which would be a strong reason to argue this should be seen as a driver for a fw interface (at least their drivers look very incompatible despite the same ICs being used)