Add TFM_EXTRA_CONFIG_PATH option in Kconfig.tfm

[jayashree505]

Is your enhancement proposal related to a problem? Please describe.
I have been trying to override some of the configurations provided by TF-M small profile. But some of these configurations are not present in Zephyr to be passed into TF-M. Also, the TFM_EXTRA_CONFIG_PATH option is not available on zephyr for me to override other options.

Describe the solution you'd like
As per TF-M's suggestion, I need to set TFM_EXTRA_CONFIG_PATH (https://tf-m-user-guide.trustedfirmware.org/configuration/build_configuration.html). The configurations in this file can override other set configuration defined by the profile or platform configurations. When building from within TF-M, this needs to passed as a command line parameter and thus it cannot be set in the other config cmake files of TF-M as well. Therefore, when building from within zephyr I would like to use this macro and therefore it needs to be added to Kconfig.tfm within zephyr.

Describe alternatives you've considered
I have tried to add this extra config path in other TF-M .cmake files, however the only way to enforce it is through the command line.

Note: Specifically I was trying to change CRYPTO_ENGINE_BUF_SIZE in the TF-M small profile. If this can be provided as a Kconfig option instead, that can be helpful too. Thanks