lib/string/strtcpy.h: Don't use a ternary op, to silence a -Wsign-compare warning

Signed-off-by: Alejandro Colomar <alx@kernel.org>

lib/string/strtcpy.h

@@ -66,7 +66,10 @@ strtcpy(char *restrict dst, const char *restrict src, size_t dsize)
 
 	stpcpy(mempcpy(dst, src, dlen), "");
 
-	return trunc ? -1 : slen;
+	if (trunc)
+		return -1;
+
+	return slen;
 }