Add components for attestation service

In preparation for implementing the attestation service provider,
building block components have been add.  This includes the
service access protocol definition, an external cbor library,
generic claim model and a concrete claim source for extracting
claims from a TCG event log.

This commit contains derived work, the following files are copied
from other projects:

components/service/attestation/claims/sources/event_log/tcg.h
   Origin:
        https://git.trustedfirmware.org/TF-A/trusted-firmware-a.git
        include/drivers/measured_boot/tcg.h
        #a5394205e94b70faf7ddd34841528ec631711d1a

components/service/attestation/include/psa/initial_attestation.h
   Origin:
        https://git.trustedfirmware.org/TF-M/trusted-firmware-m.git
        interface/include/psa/initial_attestation.h
        #9280ae9d898bffbb889e4796e51aab35a392ef82

Signed-off-by: Julian Hall <julian.hall@arm.com>
Change-Id: I5ed3e4ef7111a19b29643538ef3c47b3b6e1dd5c
diff --git a/components/common/endian/component.cmake b/components/common/endian/component.cmake
new file mode 100644
index 0000000..92d7138
--- /dev/null
+++ b/components/common/endian/component.cmake
@@ -0,0 +1,13 @@
+#-------------------------------------------------------------------------------
+# Copyright (c) 2021, Arm Limited and Contributors. All rights reserved.
+#
+# SPDX-License-Identifier: BSD-3-Clause
+#
+#-------------------------------------------------------------------------------
+if (NOT DEFINED TGT)
+	message(FATAL_ERROR "mandatory parameter TGT is not defined.")
+endif()
+
+target_sources(${TGT} PRIVATE
+	"${CMAKE_CURRENT_LIST_DIR}/le.c"
+	)