drivers: dma: Add SAM0 DMAC driver

[Sizurka]

This adds support for the SAM0 DMA Controller (DMAC).

This is a rebase and update of #6306 including implementing the new reload API and changes to support some of the updates to the DMAC found in SAME54.

Tested on SAMD21 with tests/drivers/dma/loop_transfer and custom modifications
to that test using three parallel reloading channels. Also tested
with a trivial program that did memory->serial.

@benpicco: I have compile tested this against your SAME54 branch, but if you have a chance, let me know if it works!

[zephyrbot]

All checks are passing now.

Review history of this comment for details about previous failed status.
Note that some checks might have not completed yet.

[codecov-io]

Codecov Report

Merging #14861 into master will decrease coverage by 0.31%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #14861      +/-   ##
==========================================
- Coverage   52.83%   52.52%   -0.32%     
==========================================
  Files         310      309       -1     
  Lines       45324    45063     -261     
  Branches    10476    10434      -42     
==========================================
- Hits        23947    23669     -278     
+ Misses      16590    16583       -7     
- Partials     4787     4811      +24

Impacted Files	Coverage Δ
include/spinlock.h	57.14% <0%> (-17.86%)	⬇️
kernel/mutex.c	83.82% <0%> (-13.28%)	⬇️
kernel/timeout.c	75.92% <0%> (-9.26%)	⬇️
kernel/include/kernel_structs.h	90.9% <0%> (-9.1%)	⬇️
kernel/sched.c	83.9% <0%> (-8.85%)	⬇️
include/misc/sflist.h	72.97% <0%> (-8.11%)	⬇️
include/misc/dlist.h	88.67% <0%> (-7.55%)	⬇️
kernel/sem.c	86.36% <0%> (-6.97%)	⬇️
subsys/net/ip/route.c	40.62% <0%> (-5.56%)	⬇️
kernel/thread.c	84.81% <0%> (-5.5%)	⬇️
... and 63 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c38df15...9fc4457. Read the comment docs.

[benpicco]

Nice! I've just tried it on the SAME54 and it immediately worked (tests/drivers/dma/loop_transfer) after adding the dma node to the dts.

[galak]

Looks good, one minor change to add comment about where DMAC_CHID_ID is coming from and why we might be using it (assuming this varies on different SoC variants).