modules: trusted-firmware-m: Use TF-M install headers as interface

Use the set of headers that the TF-M build system places in the
install output. Not all public header files are available in the
interface/include directory and the TF-M build system uses the install
mechanism of cmake to include additional headers based on platform
or configuration.

Signed-off-by: Joakim Andersson <joakim.andersson@nordicsemi.no>