net: Fix distro default dependencies

PING requires CMD_NET, not NET.
Also, CMD_NET already depends on NET, so no need to directly depend
on it.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

Kconfig

@@ -69,14 +69,14 @@ config DISTRO_DEFAULTS
 	imply USE_BOOTCOMMAND
 	select CMD_BOOTZ if ARM && !ARM64
 	select CMD_BOOTI if ARM64
-	select CMD_DHCP if NET && CMD_NET
+	select CMD_DHCP if CMD_NET
+	select CMD_PING if CMD_NET
 	select CMD_PXE if NET && CMD_NET
 	select CMD_EXT2
 	select CMD_EXT4
 	select CMD_FAT
 	select CMD_FS_GENERIC
 	imply CMD_MII if NET
-	select CMD_PING if NET
 	select CMD_PART if PARTITIONS
 	select HUSH_PARSER
 	select BOOTP_BOOTPATH if NET && CMD_NET