dropbear: drop obsolete patch 0004-fix-2kb-keys.patch

The origins of the patch date back to early 2005 (prior to the start
of git history in oe-core) to fix a hardcoded limit on the maximum
size of remote host keys:

  http://familiar.handhelds.narkive.com/b1VGg2bI/problem-w-dropbear-ssh

The hardcoded limit was fixed upstream in dropbear 0.47:

  https://github.com/mkj/dropbear/commit/736f370dce614b717193f45d084e9e009de723ce

The patch has therefore been obsolete since then. It went unnoticed
until now as the patch has continued to apply - it modifies a value
which is not used.

(From OE-Core rev: 17072ffc1e765edd45bc1174378fb666185e5643)

Signed-off-by: Andre McCurdy <armccurdy@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/recipes-core/dropbear/dropbear.inc

@@ -14,7 +14,6 @@ DEPENDS += "${@bb.utils.contains('DISTRO_FEATURES', 'pam', 'libpam', '', d)}"
 
 SRC_URI = "http://matt.ucc.asn.au/dropbear/releases/dropbear-${PV}.tar.bz2 \
            file://0001-urandom-xauth-changes-to-options.h.patch \
-           file://0004-fix-2kb-keys.patch \
            file://0007-fix-localoptions-search-path.patch \
            file://init \
            file://dropbearkey.service \

meta/recipes-core/dropbear/dropbear/0004-fix-2kb-keys.patch

@@ -1,19 +0,0 @@
-Subject: [PATCH 4/6] fix 2kb keys
-
-Upstream-Status: Inappropriate [configuration]
----
- kex.h | 2 +-
- 1 file changed, 1 insertion(+), 1 deletion(-)
-
-Index: dropbear-2017.75/kex.h
-===================================================================
---- dropbear-2017.75.orig/kex.h
-+++ dropbear-2017.75/kex.h
-@@ -106,6 +106,6 @@ int curve25519_donna(unsigned char *out,
- #endif
- 
- 
--#define MAX_KEXHASHBUF 2000
-+#define MAX_KEXHASHBUF 3000
- 
- #endif /* DROPBEAR_KEX_H_ */