[1.1.x] Fix Vellemann K8400 Configuration

[kaimimue]

The maximum movement is 180mm for Velleman K8400.
An offset of Y_MIN_POS violates an assertion in SanityCheck.h

Code testet on Vellemann K8400 with Dual Extruder.

[fiveangle]

I submitted a PR to fix this long ago with the Travis tests. The travis tests were rejected but I guess Scott lost this fix in the mix.

I'm pretty sure the same problem exists on the single-head 8200 so you should fix that too. I don't have the printer, but I assumed the Y_MIN_POS of 20 was correct (due to dual-head carriage) and assumed Y_MAX_POS needed to be changed. Are you confident you tested movement all the way to far bed-edge on the Y axis ?

Please review: fiveangle@16d4127

+#define Y_MAX_POS ((Y_BED_SIZE) + (Y_MIN_POS))

You have the printer, so you make the call, but just wanted to make sure that all factors were considered.

[kaimimue]

Your proposed fix is similar to my patch. In both case the y-axis can only move 180.
Why is your patch not the current version in the repository. Before my patch the movement was 200 for single head (what is wrong) and 180 for Dual-Head, but this version does not compile.