vela: Modify CFLAGS for mlw_codec makefile

Fix signed/unsigned warning
Removed from README.md as it adds no value. The standalone tool is not
expected to be used by customers.

Signed-off-by: Michael McGeagh <michael.mcgeagh@arm.com>
Change-Id: I09034478a14c37d30874d5182a096591dfdd6eb2
diff --git a/ethosu/mlw_codec/mlw_main.c b/ethosu/mlw_codec/mlw_main.c
index 9f72049..315c899 100644
--- a/ethosu/mlw_codec/mlw_main.c
+++ b/ethosu/mlw_codec/mlw_main.c
@@ -132,7 +132,7 @@
 
         if (!decode) {
             // Encode
-            int i, n = int16_format ? inbuf_size/sizeof(int16_t) : inbuf_size;
+            int i, n = int16_format ? inbuf_size/(int)sizeof(int16_t) : inbuf_size;
             int16_t *weights = malloc( n * sizeof(int16_t) );
             for(i=0; i<n; i++) {
                 weights[i] = int16_format ? ((int16_t*)inbuf)[i] : ((int8_t*)inbuf)[i];
@@ -145,7 +145,7 @@
             int i, n;
             int16_t *weights;
             n = mlw_decode( inbuf, inbuf_size, &weights, verbose);
-            outbuf_size = int16_format ? n*sizeof(int16_t) : n;
+            outbuf_size = int16_format ? n*(int)sizeof(int16_t) : n;
             outbuf = malloc( outbuf_size );
             assert(outbuf);
             for(i=0; i<n; i++) {