samsung-espresso3g: Move to community

Move Samsung Galaxy Tab 2 (7 inch) devices to community. Main reason is to let more people know about this tab, as it is very popular(having more devs isnt bad :P). There is also a 10 inch variant which is still WIP for now. Would be interesting to know how we would handle the variants as both have different displays, touchscreen, battery and sensors. There is also a 3G and WIFI variant, for now havent tested the modem, trying to get audio working first.

Wiki page: https://wiki.postmarketos.org/wiki/Samsung_Galaxy_Tab_2_7.0%22_(samsung-espresso3g). Would be better to rename it to samsung-espresso once a solution is found for variant craziness.

It does use non free stuff for PowerVR GPU.

Some issues:

• The charger smb136 is still WIP, it does charge but only when brightness is 0 (probably need to up the amps in driver?). So not upstreamed yet.
• Display is at 30Hz, at 60 Hz the display goes crazy. (Help needed to fix this)
• Brightness flickers at low values, visible when there's white background on screen. (Help needed to fix this)
• Minor nitpick: Phosh with scaling 1 is just too big enough to clip the unlock button out of touch area. Scaling to 0.75 does the trick but having decimal scaling is bad for GPU. Is it a good idea to ask upstream phosh to do something?