drm/amd/display: clean up a condition in dmub_psr_copy_settings()

We can remove the NULL check for "res_ctx" and
"res_ctx->pipe_ctx[i].stream->link".  Also it's nicer to align the
conditions using spaces so I re-indented a bit.

Longer explanation: The "res_ctx" pointer points to an address in the
middle of a struct so it can't be NULL.  For
"res_ctx->pipe_ctx[i].stream->link" we know that it is equal to "link"
and "link" is non-NULL.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>