Add locks to R-Car PFC driver

[xakep-amatop]

To prevent the R-Car PFC driver from functioning incorrectly, it is necessary to add locks. For instance, if a thread happens to call the pfc_rcar_write function and then goes to sleep between two writes, the value in PMMR can be overwritten by another thread:

	sys_write32(~val, PFC_REG_BASE + PFC_RCAR_PMMR);
	sys_write32(val, PFC_REG_BASE + offs);

To address this issue and similar situations within the driver, proper protection should be implemented.

Furthermore, there can be an issue when attempting to modify the PFC state on multi-core systems.

[github-actions]

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[xakep-amatop]

Note: perhaps it would be even better to add locks to the common PFC drivers API, although it may require making numerous changes to other PFC drivers.

[zephyrbot]

Hi @lorc, @aaillet,

This issue, marked as an Enhancement, was opened a while ago and did not get any traction. It was just assigned to you based on the labels. If you don't consider yourself the right person to address this issue, please re-assing it to the right person.

Please take a moment to review if the issue is still relevant to the project. If it is, please provide feedback and direction on how to move forward. If it is not, has already been addressed, is a duplicate, or is no longer relevant, please close it with a short comment explaining the reason.

@xakep-amatop you are also encouraged to help moving this issue forward by providing additional information and confirming this request/issue is still relevant to you.

Thanks!