[3.18] main/dropbear: add mitigations for CVE-2023-48795
https://github.com/mkj/dropbear/commit/66bc1fcdee594c6cb1139df0ef8a6c9c5fc3fde3
Implement-Strict-KEX-mode.patch is 's,/src/,/,g' modified https://github.com/mkj/dropbear/commit/6e43be5c7b99dbee49dc72b6f989f29fdd7e9356