tests: remove usage of MBEDTLS_NO_PLATFORM_ENTROPY

Use MBEDTLS_PLATFORM_GET_ENTROPY_ALT instead.

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/scripts/footprint.sh b/scripts/footprint.sh
index 614a493..e45a926 100755
--- a/scripts/footprint.sh
+++ b/scripts/footprint.sh
@@ -64,7 +64,7 @@
         scripts/config.py unset MBEDTLS_NET_C || true
         scripts/config.py unset MBEDTLS_TIMING_C || true
         scripts/config.py unset MBEDTLS_FS_IO || true
-        scripts/config.py --force set MBEDTLS_NO_PLATFORM_ENTROPY || true
+        scripts/config.py --force set MBEDTLS_PLATFORM_GET_ENTROPY_ALT || true
     } >/dev/null 2>&1
 
     make clean >/dev/null