Merge changes from topic "fw-update-2" into integration
* changes:
feat(sw_crc32): add software CRC32 support
refactor(hw_crc32): renamed hw_crc32 to tf_crc32
feat(fwu): avoid booting with an alternate boot source
docs(fwu): add firmware update documentation
feat(fwu): avoid NV counter upgrade in trial run state
feat(plat/arm): add FWU support in Arm platforms
feat(fwu): initialize FWU driver in BL2
feat(fwu): add FWU driver
feat(fwu): introduce FWU platform-specific functions declarations
docs(fwu_metadata): add FWU metadata build options
feat(fwu_metadata): add FWU metadata header and build options