build: scripts/config - update to kconfig-v6.6.16

The main goal here is to keep this close to upstream.

Changes include:
 - allow symbols implied by y to become m
 - make 'imply' obey the direct dependency
 - allow only 'config', 'comment', and 'if' inside 'choice'
 - qconf: make search fully work again on split mode
 - qconf: navigate menus on hyperlinks
 - remove '---help---' support
 - qconf: allow to edit "int", "hex", "string" menus in-place
 - qconf: drop Qt4 support
 - nconf: fix core dump when searching in empty menu
 - nconf: stop endless search loops
 - Create links to main menu items in search
 - fix segmentation fault in menuconfig search
 - nconf: Add search jump feature
 - port qconf to work with Qt6 in addition to Qt5
 - fix possible buffer overflow
 - fix memory leak from range properties

Signed-off-by: Eneas U de Queiroz <cotequeiroz@gmail.com>

scripts/config/README

@@ -1,6 +1,7 @@
-These files were taken from the Linux 5.14 Kernel Configuration System and
-modified for the OpenWrt Buildroot:
- - Removed nconf, gconf, tests and kernel configuration targets.
+These files were taken from the Linux Kernel Configuration System v6.6.16, 
+at commit eb3e299184cc4f40d4bd84fda269b3a20ddcff80 (Feb 5, 2024),  and modified
+for the OpenWrt Buildroot:
+ - Removed gconf, tests and kernel configuration targets.
  - Adjusted the Makefile to compile outside the kernel.
  - Always use default file when running make all{no,mod,yes}config.
  - Added a 'reset' command to reset config when the target changes.
@@ -23,4 +24,4 @@ modified for the OpenWrt Buildroot:
    BUILD_SHIPPED_FILES defined
 
 For a full list of changes, see the repository at:
-https://github.com/cotequeiroz/linux/commits/openwrt-5.14/scripts/kconfig
+https://github.com/cotequeiroz/linux/commits/openwrt-v6.6.16/scripts/kconfig