libssh: correct libssh src file list

Link against the ssh-sk-helper client rather than the sk internal
implementation.

PR:		258384
Tested by:	madpilot
Fixes:		f448c3e ("openssh: Add new source files to libssl")
Fixes:		1926107 ("openssh: update to OpenSSH v8.7p1")
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D32529

secure/lib/libssh/Makefile

@@ -5,7 +5,7 @@
 LIB=	ssh
 PRIVATELIB=	true
 SHLIB_MAJOR=	5
-SRCS=	ssh_api.c ssh-sk.c ssh-ecdsa-sk.c ssh-ed25519-sk.c ssherr.c \
+SRCS=	ssh_api.c ssh-sk-client.c ssh-ecdsa-sk.c ssh-ed25519-sk.c ssherr.c \
 	sshbuf.c sshkey.c sshbuf-getput-basic.c \
 	sshbuf-misc.c sshbuf-getput-crypto.c krl.c bitmap.c
 SRCS+=	authfd.c authfile.c \