add board support for QMTech XC7A35T core board and daughterboard

[hansfbaier]

Just got my board today, and blinky test of all 6 leds and buttons works.
The LEDs and buttons are on the baseboard, which means the pin mappings are good.

[hansfbaier]

Here is a short video of the blinky: https://twitter.com/hansfbaier/status/1387664548660858883

[whitequark]

Please put all of these into a single toplevel qmtech_xc7a35t module; they're a part of one kit.

[hansfbaier]

@whitequark The Daughterboard is useable independently and can be used with a number of other QMTech daughterboards, see https://qmtechchina.aliexpress.com/store/4486047?spm=a2g0o.productlist.0.0.21785a1f82fPyk
Factoring out the daughterboard allows to plug in all the other core boards.

[whitequark]

Hm, I'll need to think of the best way to handle this, then.

[hansfbaier]

Also we need the option to use the core boards independently of the daughterboard

[hansfbaier]

Also need to consider the similar case of standardized boards like feather (OrangeCrab), pmod, etc.
Would be great to have some generic infrastructure to plug those into own projects in a uniform way.

[whitequark]

There is support for pmods already.

[hansfbaier]

Ah yes, sorry, I remember now.

[hansfbaier]

@whitequark I got rid of QMTechXC7A35TKitPlatform and added the daughterboard as an option to the main platform file

[hansfbaier]

@whitequark Will close this request and open another one with the QMTech EP4CE15 board included