shader: TESSCOORD is handled as sysvalue

There is no need to handle it as input or output.

Signed-off-by: Gert Wollny <gert.wollny@collabora.com>
Part-of: <!847>
17 jobs for !847 with shader-cleanups in 23 minutes and 41 seconds (queued for 2 minutes and 32 seconds)
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