GPU-DRM-TILCDC: Less function calls in tilcdc_convert_slave_node() after error detection

[SF Markus Elfring]

> iirc, there are Coccinelle rules that find code with unnecessary null
> checks and removes them.

This kind of software change is not needed here.

I find that a corresponding return value check happens one function call
too late.


> Although you probably made this complex enough that cocinelle would
> not find it.  That is not a complement.

I imagine that scripts for the semantic patch language can find more
source code places where questionable disjunctions are used so far.
Would you dare to split any more condition checks?


> One should not make error handling/cleanup more complex than needed.

I see a need to improve not only correctness there but also a bit of
software efficiency.

Regards,
Markus