lib : tinycrypt : Adding README for external library

Adding in a README file for the external library of TinyCrypt providing
details for origin, commit id, and where to find the original.

Source: Original to Zephyr Project

Change-Id: Ibc7ec33f7f459e8df88978b5b4505e67a2141998
Signed-off-by: Dan Kalowsky <daniel.kalowsky@intel.com>

lib/crypto/tinycrypt/README

@@ -0,0 +1,47 @@
+The TinyCrypt library in Zephyr is a downstream of an externally maintained
+open source project.  The original upstream code can be found at:
+
+https://github.com/01org/tinycrypt
+
+At revision 08ded7f21529c39e5133688ffb93a9d0c94e5c6e
+
+Any changes to the local version should include Zephyr's TinyCrypt
+maintainer in the review.  That can be found via the git history.
+
+The following is the license information for this code:
+
+================================================================================
+
+                     TinyCrypt Cryptographic Library v1.0
+
+================================================================================
+
+          Copyright (c) 2015, Intel Corporation. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without modification,
+are permitted provided that the following conditions are met:
+
+  - Redistributions of source code must retain the above copyright notice, this
+      list of conditions and the following disclaimer.
+
+  - 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.
+
+  - Neither the name of the Intel Corporation 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 OWNER 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.
+
+================================================================================