dropbear: use ssh-keygen as an alias for dropbearkey

The DropBear's dropbearkey supports limited set of arguments of
OpenSSH ssh-keygen:  -t, -q -N -Y
After the change you can generate a key with the same command.
Still many features of the original OpenSSH ssh-keygen are absent in
the dropbearkey.
If it's needed then users should install openssh-keygen package that
will replace the /usr/bin/ssh-keygen with the full version.

Signed-off-by: Sergey Ponomarev <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/14174
[ wrap commit description to 80 columns ]
Link: https://github.com/openwrt/openwrt/pull/14174
Signed-off-by: Christian Marangi <[email protected]>

package/network/services/dropbear/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=dropbear
 PKG_VERSION:=2022.83
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_SOURCE:=$(PKG_NAME)-$(PKG_VERSION).tar.bz2
 PKG_SOURCE_URL:= \
@@ -57,7 +57,7 @@ define Package/dropbear
   CATEGORY:=Base system
   TITLE:=Small SSH2 client/server
   DEPENDS:= +DROPBEAR_ZLIB:zlib
-  ALTERNATIVES:=
+  ALTERNATIVES:=100:/usr/bin/ssh-keygen:/usr/sbin/dropbear
   $(if $(CONFIG_DROPBEAR_SCP),ALTERNATIVES+= \
 	  100:/usr/bin/scp:/usr/sbin/dropbear,)
   $(if $(CONFIG_DROPBEAR_DBCLIENT),ALTERNATIVES+= \