sys: move sys/kern/md[45].c to sys/crypto

Both files are used by kernel and userspace.
Move them to sys/crypto where they belong.

No functional changes intended.

In preparation of D45670.

Reviewed by:	markj
Approved by:	markj (mentor)
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D52909

lib/libmd/Makefile

@@ -108,7 +108,7 @@ CFLAGS+= -DWEAK_REFS
 CFLAGS.skein_block.c+= -DSKEIN_LOOP=995
 .PATH: ${.CURDIR}/${MACHINE_ARCH} ${SRCTOP}/sys/crypto/sha2
 .PATH: ${SRCTOP}/sys/crypto/skein ${SRCTOP}/sys/crypto/skein/${MACHINE_ARCH}
-.PATH: ${SRCTOP}/sys/kern
+.PATH: ${SRCTOP}/sys/crypto
 
 USE_ASM_SOURCES?=1
 .if defined(BOOTSTRAPPING) || ${MK_MACHDEP_OPTIMIZATIONS} == no

stand/libsa/Makefile

@@ -189,8 +189,7 @@ SRCS+=	g_eli_hmac.c pkcs5v2.c
 .PATH: ${SYSDIR}/crypto/sha2
 SRCS+=		sha256c.c sha512c.c
 
-# md5 from the kernel
-.PATH: ${SYSDIR}/kern
+.PATH: ${SYSDIR}/crypto
 SRCS+=		md5c.c
 
 .if ${DO32:U0} == 0

sys/conf/files

@@ -681,6 +681,8 @@ crypto/curve25519.c		optional crypto \
 	compile-with "${NORMAL_C} -I$S/contrib/libsodium/src/libsodium/include -I$S/crypto/libsodium"
 crypto/des/des_ecb.c		optional netsmb
 crypto/des/des_setkey.c		optional netsmb
+crypto/md4c.c			optional netsmb
+crypto/md5c.c			standard
 crypto/openssl/ossl.c		optional ossl
 crypto/openssl/ossl_aes.c	optional ossl
 crypto/openssl/ossl_chacha20.c	optional ossl
@@ -3896,8 +3898,6 @@ kern/kern_vnodedumper.c		standard
 kern/kern_xxx.c			standard
 kern/link_elf.c			standard
 kern/linker_if.m		standard
-kern/md4c.c			optional netsmb
-kern/md5c.c			standard
 kern/p1003_1b.c			standard
 kern/posix4_mib.c		standard
 kern/sched_4bsd.c		optional sched_4bsd

sys/modules/smbfs/Makefile

@@ -1,6 +1,6 @@
-.PATH:	${SRCTOP}/sys/crypto/des \
+.PATH:	${SRCTOP}/sys/crypto \
+	${SRCTOP}/sys/crypto/des \
 	${SRCTOP}/sys/crypto/des/arch/${MACHINE_CPUARCH} \
-	${SRCTOP}/sys/kern \
 	${SRCTOP}/sys/libkern \
 	${SRCTOP}/sys/netsmb \
 	${SRCTOP}/sys/fs/smbfs