bootmenu: U-Boot console is enabled as default

bootmenu: U-Boot console is enabled as default

The commit 2158b0da220c ("bootmenu: add Kconfig option
not to enter U-Boot console") disables to enter U-Boot
console from bootmenu as default, this change affects the
existing bootmenu users.

This commit reverts the default behavior, the bootmenu can
enter U-Boot console same as before.
CMD_BOOTMENU_ENTER_UBOOT_CONSOLE is renamed
BOOTMENU_DISABLE_UBOOT_CONSOLE and depends on
AUTOBOOT_MENU_SHOW.

Fixes: 2158b0da220c ("bootmenu: add Kconfig option not to enter U-Boot console")
Signed-off-by: Masahisa Kojima <[email protected]>
Tested-by: Pali Rohar <[email protected]>
Reviewed-by: Ilias Apalodimas <[email protected]>
Reviewed-by: Heinrich Schuchardt <[email protected]>