TF-M: increase default Mbed TLS heap size in TF-M

[valeriosetti]

This PR updates the TF-M reference in to include a couple of commits which are useful to properly size the heap memory allocated in TF-M for the crypto partition. This is necessary in order to allow Mbed TLS to handle RSA signatures with 2048-bits (previously only 1024-bits were possible).

Resolves #79864

[zephyrbot]

The following west manifest projects have changed revision in this Pull Request:

Name	Old Revision	New Revision	Diff
trusted-firmware-m	zephyrproject-rtos/trusted-firmware-m@bceac6c	zephyrproject-rtos/trusted-firmware-m@fa020a8 (main)	zephyrproject-rtos/[email protected]

✅ All manifest checks OK

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[valeriosetti]

Since GH did not automatically assigned reviewers to this PR, I manually added @ithinuel, @tomi-font, @d3zd3z, @Vge0rge as reported in the MAINTAINERS.yml file.

[d3zd3z]

So, this seems reasonable, at least as far as RSA goes, but do you know where the requirement for RSA at all is coming from?

[valeriosetti]

So, this seems reasonable, at least as far as RSA goes, but do you know where the requirement for RSA at all is coming from?

If you meant "who is willing to use RSA signatures with 2048-bits" then I was notified by this issue #79864.

Instead if your question was more like "why RSA needs so much heap memory", it's because TF-M uses Mbed TLS in its crypto partition to perform crypto operations and there RSA uses heap memory a lot (through bignum module, in case you are curious).

Luckily the TF-M team already spotted this issue recently and they already had a fix for it, so it was quite easy for me to cherry-pick the fix from them.

@d3zd3z did I answered your question?

[tomi-font]

Please change at least the title of the commit to be more explicit about what this is for than update reference.

[valeriosetti]

I had to rebase to solve a conflict on west.yml. Please re-check :)