[TF-M] Please review the patch set to extract duplicated template files from platforms

Hi all,

I submit a patch set to extract the duplicated identical template files dummy_xxx.c from targets and put them under platform/ext/common/template folder. The purpose is to collect a common template of booting/attestation example for platforms and each platform doesn't need to keep a copy under its folder anymore.

Since it is a general change related to all platforms using template files, I'd like to ask for review here. Any comments would be appreciated. Please check the patch details in https://review.trustedfirmware.org/q/topic:%22template_plat_files%22+(status...) The background is described in https://developer.trustedfirmware.org/T539.

Best regards, Hu Ziji