Add BSD 2c license to sdcard driver

drivers/sdcard/LICENSE

@@ -0,0 +1,22 @@
+    Copyright (c) 2020-2021, Elehobica
+
+    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.
+
+    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.

drivers/sdcard/README.md

@@ -2,4 +2,6 @@
 
 All of the hard work to bring up these bindings was done by @elohobica - https://github.com/elehobica/pico_fatfs_test
 
-`sdcard.c` is a hard fork of their `tf_card.c` to add re-usable SDCard support to the Pimoroni Pico libraries.
+`sdcard.c` is a hard fork of their `tf_card.c` to add re-usable SDCard support to the Pimoroni Pico libraries.
+
+It's licensed under the BSD 2-Clause license.