Add BSD3-clause license file to TF-M folder

LICENSE

@@ -5,6 +5,7 @@ Folders containing files under different permissive license than Apache 2.0 are
 
 - [cmsis](./cmsis) - MIT, BSD-3-Clause
 - [components/802.15.4_RF/mcr20a-rf-driver](./components/802.15.4_RF/mcr20a-rf-driver) - BSD-3-Clause
+- [components/TARGET_PSA/TARGET_TFM](./components/TARGET_PSA/TARGET_TFM) - BSD-3-Clause
 - [features/cryptocell/FEATURE_CRYPTOCELL310](./features/cryptocell/FEATURE_CRYPTOCELL310) - ARM Object Code and Header Files License
 - [features/FEATURE_BOOTLOADER](./features/FEATURE_BOOTLOADER) - PBL
 - [features/FEATURE_BLE/targets](./features/FEATURE_BLE/targets) - BSD-style, PBL, MIT-style

components/TARGET_PSA/TARGET_TFM/LICENSE

@@ -0,0 +1,2 @@
+Unless specifically indicated otherwise in a file, TF-M files in this directory are licensed under the BSD-3-Clause license,
+as can be found in: LICENSE-bsd-3-clause.txt

components/TARGET_PSA/TARGET_TFM/LICENSE-BSD-3-Clause

@@ -0,0 +1,26 @@
+Copyright 2019 Arm Limited and affiliates.
+SPDX-License-Identifier: BSD-3-Clause
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+1. Redistributions of source code must retain the above copyright
+   notice, this list of conditions and the following disclaimer.
+2. Redistributions in binary form must reproduce the above copyright
+   notice, this list of conditions and the following disclaimer in the
+   documentation and/or other materials provided with the distribution.
+3. Neither the name of the copyright holder nor the
+   names of its contributors may be used to endorse or promote products
+   derived from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS \"AS IS\"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.