Nouveau - May 2020 - drm/nouveau/clk/gm20b: Fix memory leaks after failed gk20a_clk_ctor() calls

> > If gk20a_clk_ctor() never returns such an error code,
> > we may need not to release this clock object.
> 
> Would you like to achieve complete exception handling
> also for this function implementation?
> 
It seems that it's possible to get -ENOMEM from gk20a_clk_ctor().
The call chain is as follows:
gk20a_clk_ctor() <- nvkm_clk_ctor() <- nvkm_notify_init()

When nvkm_notify_init() returns -ENOMEM, all of its callers (and 
callers of callers) will be influenced if there is a failed
kzalloc inside which. 

In this case, maybe we should check the return value of 
gk20a_clk_ctor() and release clk if it returns -ENOMEM. 
And many other functions also have the same issue (e.g.,
gm20b_clk_new_speedo0). Do you have any idea about this 
problem?

Regards,
Dinghao

> In this case, maybe we should check the return value of
> gk20a_clk_ctor() and release clk if it returns -ENOMEM.
All error situations (including failed memory allocations) can matter here.

> And many other functions also have the same issue
> (e.g. gm20b_clk_new_speedo0).
I recommend to increase the error detection and improve the desired
exception handling accordingly.

Regards,
Markus