dai-zephyr: do not set local buffer if no process func found

[kv2019i]

Rework set_new_local_buffer() to not set dd->local_buffer multiple times.

[kv2019i]

Not sure @lyakh this helps much, but we do avoid one extra dd->local_buffer write.

[juimonen]

not sure I understand the optimization, but looks innocent enough to me

[lyakh]

looks good, thanks for fixing it! But need to fix one hick up.

[lyakh]

@kv2019i@juimonen Given two possibilities:

	never_fails();
ret = might_fail();
if (ret < 0) {
undo_never_fails();
return ret;
}

and

	ret = might_fail();
if (ret < 0)
return ret;
never_fails();

as long as the order indeed isn't important - often both will work correctly, but I think one is clearly preferable over the other and should be used whenever possible.

[kv2019i]

V2 uploaded, please review.

[kv2019i]

The Intel CI System/merge/build fails to one run of "TestSrcFullScope::test_01_04_src" indicating a glitch on one platform. I don't think it can be related to this PR, but need to do another run to be sure.

[lgirdwood]

SOFCI TEST

[lgirdwood]

@kv2019i still failing CI, can you check. Thanks