drm/amd/powerplay: remove unnecessary call to memset

call to memset to assign 0 value immediately after allocating
memory with kzalloc is unnecesaary as kzalloc allocates the memory
filled with 0 value.

Semantic patch used to resolve this issue:

@@
expression e,e2; constant c;
statement S;
@@

  e = kzalloc(e2, c);
  if(e == NULL) S
- memset(e, 0, e2);

Signed-off-by: Himanshu Jha <himanshujha199640@gmail.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>