net: Move the CMD_NET config to defconfigs

This also selects CONFIG_NET for any CONFIG_CMD_NET board.

Remove the imx default for CONFIG_NET.

This moves the config that was defined by 60296a8 (commands: add more
command entries in Kconfig).

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/configs/tqma6q_mba6_mmc_defconfig b/configs/tqma6q_mba6_mmc_defconfig
index 772a379..01355b6 100644
--- a/configs/tqma6q_mba6_mmc_defconfig
+++ b/configs/tqma6q_mba6_mmc_defconfig
@@ -2,3 +2,4 @@
 CONFIG_TARGET_TQMA6=y
 CONFIG_SYS_EXTRA_OPTIONS="IMX_CONFIG=board/tqc/tqma6/tqma6q.cfg,MX6Q,MBA6,TQMA6X_MMC_BOOT"
 CONFIG_CMD_SETEXPR=y
+CONFIG_CMD_NET=y