Rename CONFIG_SYS_AUTOLAOD to CONFIG_SYS_DISABLE_AUTOLOAD

The "autoload" environment variable is always checked with env_get_yesno
as it can be set to any form of no.  The default behavior of
env_get_yesno is to return -1 on variables that are not set, which acts
as true in general (we test for non-zero return).  To convert
CONFIG_SYS_AUTOLOAD to Kconfig, given that it was almost always used to
set autoload to no, first rename to CONFIG_SYS_DISABLE_AUTOLOAD for
consistency sake.  Then, make it so that if enabled we set autoload=0 in
the default environment.  Migrate all platforms which set
CONFIG_SYS_AUTOLOAD to non-true or that set autoload to false in their
default environment to using CONFIG_SYS_DISABLE_AUTOLOAD

Signed-off-by: Tom Rini <trini@konsulko.com>

cmd/Kconfig

@@ -1737,6 +1737,15 @@ config NFS_TIMEOUT
 	  "ERROR: Cannot umount" in nfs command, try longer timeout such as
 	  10000.
 
+config SYS_DISABLE_AUTOLOAD
+	bool "Disable automatically loading files over the network"
+	depends on CMD_BOOTP || CMD_DHCP || CMD_NFS || CMD_RARP
+	help
+	  Typically, commands such as "dhcp" will attempt to automatically
+	  load a file from the network, once the initial network configuration
+	  is complete.  Enable this option to disable this behavior and instead
+	  require files to be loaded over the network by subsequent commands.
+
 config CMD_MII
 	bool "mii"
 	imply CMD_MDIO