freedom-k64f/demo: Support Ethernet

It was tested using:

  nsh> ifconfig
  eth0    Link encap:Ethernet HWaddr 52:13:FF:FF:FF:FF at DOWN
          inet addr:10.0.0.2 DRaddr:10.0.0.1 Mask:255.255.255.0

All flags are needed to prevent build failures like:

    chip/kinetis_enet.c:181:4:\
    error: #error "Unrecognized or missing PHY selection"

    netlib_setifstatus.c: In function 'netlib_ifup':
    netlib_setifstatus.c:83:27: \
    error: 'NETLIB_SOCK_TYPE' undeclared (first use in this function);

Change-Id: I9496528ae09f6244d73ab77dbcd307ced95f46fd
Bug: https://github.com/apache/incubator-nuttx/pull/1988
Forwarded: https://github.com/apache/incubator-nuttx/pull/2066
Signed-off-by: Philippe Coval <rzr@users.sf.net>

boards/arm/kinetis/freedom-k64f/configs/demo/defconfig

@@ -21,6 +21,7 @@ CONFIG_DEBUG_SYMBOLS=y
 CONFIG_DISABLE_ENVIRON=y
 CONFIG_DISABLE_MQUEUE=y
 CONFIG_DISABLE_POSIX_TIMERS=y
+CONFIG_ETH0_PHY_KSZ8081=y
 CONFIG_EXAMPLES_FXOS8700CQ=y
 CONFIG_EXAMPLES_PWM=y
 CONFIG_FAT_LCNAMES=y
@@ -29,6 +30,7 @@ CONFIG_FS_FAT=y
 CONFIG_FS_PROCFS=y
 CONFIG_FS_PROCFS_REGISTER=y
 CONFIG_INTELHEX_BINARY=y
+CONFIG_KINETIS_ENET=y
 CONFIG_KINETIS_FTM0=y
 CONFIG_KINETIS_FTM0_CHANNEL=2
 CONFIG_KINETIS_FTM0_PWM=y
@@ -42,6 +44,7 @@ CONFIG_MMCSD=y
 CONFIG_MMCSD_MULTIBLOCK_DISABLE=y
 CONFIG_MMCSD_SDIO=y
 CONFIG_MOTOROLA_SREC=y
+CONFIG_NET_UDP=y
 CONFIG_NFILE_DESCRIPTORS=8
 CONFIG_NSH_ARCHINIT=y
 CONFIG_NSH_BUILTIN_APPS=y