mbedtls: update to 3.6.6

This version fixes some security problems:
 * Client impersonation while resuming a TLS 1.3 session
   (CVE-2026-34873)
 * Entropy on Linux can fall back to /dev/urandom (CVE-2026-34871)
 * PSA random generator cloning (CVE-2026-25835)
 * Compiler-induced constant-time violations (CVE-2025-66442)
 * Null pointer dereference when setting a distinguished name
   (CVE-2026-34874)
 * Buffer overflow in FFDH public key export (CVE-2026-34875)
 * FFDH: lack of contributory behaviour due to improper input validation
   (CVE-2026-34872)
 * Signature Algorithm Injection (CVE-2026-25834)
 * CCM multipart finish tag-length validation bypass (CVE-2026-34876)
 * Risk of insufficient protection of serialized session or context data
   leading to potential memory safety issues (CVE-2026-34877)
 * Buffer underflow in x509_inet_pton_ipv6() (CVE-2026-25833)

Changelog: https://github.com/Mbed-TLS/mbedtls/releases/tag/mbedtls-3.6.6

Size increases by 470 bytes on aarch64:
343995 bin/packages/aarch64_generic/base/libmbedtls21-3.6.5-r1.apk
344465 bin/packages/aarch64_generic/base/libmbedtls21-3.6.6-r1.apk

Link: https://github.com/openwrt/openwrt/pull/22787
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
(cherry picked from commit f48ef0040b)

package/libs/mbedtls/Makefile

@@ -8,13 +8,13 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mbedtls
-PKG_VERSION:=3.6.5
+PKG_VERSION:=3.6.6
 PKG_RELEASE:=1
 PKG_BUILD_FLAGS:=no-mips16 gc-sections no-lto
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL=https://github.com/Mbed-TLS/$(PKG_NAME)/releases/download/$(PKG_NAME)-$(PKG_VERSION)
-PKG_HASH:=4a11f1777bb95bf4ad96721cac945a26e04bf19f57d905f241fe77ebeddf46d8
+PKG_HASH:=8fb65fae8dcae5840f793c0a334860a411f884cc537ea290ce1c52bb64ca007a
 
 PKG_LICENSE:=GPL-2.0-or-later
 PKG_LICENSE_FILES:=LICENSE

package/libs/mbedtls/patches/100-fix-gcc14-build.patch

@@ -1,6 +1,6 @@
 --- a/library/common.h
 +++ b/library/common.h
-@@ -199,7 +199,7 @@ static inline void mbedtls_xor(unsigned
+@@ -224,7 +224,7 @@ static inline void mbedtls_xor(unsigned
          uint8x16_t x = veorq_u8(v1, v2);
          vst1q_u8(r + i, x);
      }