Change in coreboot[master]: soc/rockchip/rk3399/sdram: Clear PI_175 IRQs in data training

[Moritz Fischer (Code Review)]

Attention is currently required from: Angel Pons, Julius Werner.
Moritz Fischer has posted comments on this change. ( https://review.coreboot.org/c/coreboot/+/50886 )

Change subject: soc/rockchip/rk3399/sdram: Clear PI_175 IRQs in data training
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Patch Set 1:

(1 comment)

Commit Message:

https://review.coreboot.org/c/coreboot/+/50886/comment/e4433317_16154270 
PS1, Line 10: calls.
> Is this to ensure training will work properly? It would be nice to mention why this is necessary.

I couldn't figure out how to add a 'cover letter'.

I'm mostly porting stuff from U-Boot. Maybe I should make one giant series instead for better context. I'm trying to do the non-invasive small changes first.