[RFC][WIP] zephyr: extract heap management

[lyakh]

A draft for IMX / cAVS splitting. In fact the difference is very small, maybe we can keep a large portion of this common. This is just a quick RFC, suggestions?

[iuliana-prodan]

@lyakh I don't think we should split this into 2 files, for imx and cavs - there is a lot of duplicated code.

I was thinking of keeping the #ifdef CONFIG_IMX at line 34, since we, for imx, need the heapmem variable in a different section.

The next part, the #else (starting with line 41) I believe it should be split into SMP and non-SMP.
For imx we only need non-SMP, APL has also 1 core, so there is no need for heapmem and heapmem_shared or sof_heap and sof_heap_shared- no need to split heap into shared and unshared.
The shared variables should be declared only for SMP. Please, correct me if I'm wrong.

I've tested only with sof_heap on imx and also @marc-hb verified on APL - see comment here.

In the rest of the file, where we use sof_heap_shared, should be under #ifdef CONFIG_SMP - in functions like statics_init(), rmalloc(), rfree().

[marc-hb]

@lyakh I don't think we should split this into 2 files, for imx and cavs - there is a lot of duplicated code.

Agreed right now there's way too much duplication, copy/paste/diverge is unmaintainable. The alloc_platform.c files (if really needed) should be much smaller and all the rest in a new alloc_common.c. Large #ifdef suck because they require reading two different flows merged into one which is cognitive strain and error-prone. On the other hand, when there is only a small #ifdef then it's better to keep 90% identical functions in alloc_common.c instead of duplicating these 90%.