debug: remove redundant variable assignments

Signed-off-by: Valerio Setti <valerio.setti@nordicsemi.no>
diff --git a/library/debug.c b/library/debug.c
index 92fe903..c392f63 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -144,7 +144,6 @@
 
     debug_send_line(ssl, level, file, line, str);
 
-    idx = 0;
     memset(txt, 0, sizeof(txt));
     for (i = 0; i < len; i++) {
         if (i >= 4096) {
@@ -215,7 +214,6 @@
 
     debug_send_line(ssl, level, file, line, str);
 
-    idx = 0;
     for (i = 0; i < len; i++) {
         if (i >= 4096) {
             break;