Call in_mbedtls_repo

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/scripts/lcov.sh b/scripts/lcov.sh
index 516d9e3..2d2f42b 100755
--- a/scripts/lcov.sh
+++ b/scripts/lcov.sh
@@ -74,7 +74,7 @@
     exit
 fi
 
-if in_mbedtls_build_dir; then
+if in_mbedtls_repo; then
     library_dir='library'
     title='Mbed TLS'
 else