autoboot: Rename CONFIG_MENUKEY to CONFIG_AUTOBOOT_MENUKEY

Since this is part of the autoboot functionality, it makes sense to name
it with an AUTOBOOT prefix. No mainline boards use it so this should be
safe, and downstream boards will need to adjust.

Since this option is just an integer value, it really needs another option
to control whether the feature is enabled or not. Add a new
CONFIG_USE_AUTOBOOT_MENUKEY for that. This fits better with how things are
done with Kconfig, avoiding the need to use a specific value to disable
the feature.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/socfpga_vining_fpga_defconfig b/configs/socfpga_vining_fpga_defconfig
index 1a9323f..9e86a23 100644
--- a/configs/socfpga_vining_fpga_defconfig
+++ b/configs/socfpga_vining_fpga_defconfig
@@ -8,7 +8,7 @@
 CONFIG_BOOTARGS="console=ttyS0,115200"
 # CONFIG_USE_BOOTCOMMAND is not set
 CONFIG_USE_PREBOOT=y
-CONFIG_PREBOOT="setenv hostname vining-${unit_serial} ; setenv PS1 "${unit_ident} (${unit_serial}) => " ; if gpio input 78 ; then setenv bootdelay 10 ; setenv boottype rcvr ; else setenv bootdelay 5 ; setenv boottype norm ; fi"
+CONFIG_PREBOOT="setenv hostname vining-${unit_serial} ; setenv PS1 \"${unit_ident} (${unit_serial}) => \" ; if gpio input 78 ; then setenv bootdelay 10 ; setenv boottype rcvr ; else setenv bootdelay 5 ; setenv boottype norm ; fi"
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
 CONFIG_SYS_CONSOLE_OVERWRITE_ROUTINE=y
 CONFIG_SYS_CONSOLE_ENV_OVERWRITE=y