Remove Yotta support from the docs, tests and build scripts

Yotta is no longer supported by Mbed TLS, so has been removed. Specifically, the
following changes have been made:
 * references to yotta have been removed from the main readme and build
   instructions
 * the yotta module directory and build script has been removed
 * yotta has been removed from test scripts such as all.sh and check-names.sh
 * yotta has been removed from other files that that referenced it such as the
   doxyfile and the bn_mul.h header
 * yotta specific configurations and references have been removed from config.h
diff --git a/tests/scripts/check-names.sh b/tests/scripts/check-names.sh
index 4c66440..f18a162 100755
--- a/tests/scripts/check-names.sh
+++ b/tests/scripts/check-names.sh
@@ -40,7 +40,7 @@
 for THING in actual-macros enum-consts; do
     printf "Names of $THING: "
     test -r $THING
-    BAD=$( grep -v '^MBEDTLS_[0-9A-Z_]*[0-9A-Z]$\|^YOTTA_[0-9A-Z_]*[0-9A-Z]$' $THING || true )
+    BAD=$( grep -v '^MBEDTLS_[0-9A-Z_]*[0-9A-Z]$' $THING || true )
     if [ "x$BAD" = "x" ]; then
         echo "PASS"
     else