sms: fix warning and remove old logic

> Warning: libsms_getsms.c:107:25: warning: implicit conversion from 'int' to 'char' changes value from 183 to -73 [-Wconstant-conversion]
>   107 |                         ascii[charcounter] = 183;
>       |                                            ~ ^~~
> 1 warning generated.

(cherry picked from commit ee052fd0a7e7dc703a186a01926a8e64c635d636)

src/modules/sms/libsms_getsms.c

@@ -101,12 +101,7 @@ static int pdu2ascii(char *pdu, char *ascii)
 			bitposition++;
 			c = (c >> 1) & 127; /* The shift fills with 1, but I want 0 */
 		}
-		if(/*cs_convert*/ 1)
-			ascii[charcounter] = sms2ascii(c);
-		else if(c == 0)
-			ascii[charcounter] = 183;
-		else
-			ascii[charcounter] = c;
+		ascii[charcounter] = sms2ascii(c);
 	}
 	ascii[count] = 0;
 	return count;