sunxi: kconfig: Introduce CONFIG_TARGET_<BOARD>

This was done automatically with the following bits of scripting.

The Kconfig choice content was generated with this script snippet:
    for i in $(git grep -l CONFIG_ARCH_SUNXI configs/*) ; do
        TARGET=$(sed -n -e 's/CONFIG_SYS_EXTRA_OPTIONS="\([^,"]\+\).*/\1/p' $i);
        MACH=$(sed -n -e 's/.*CONFIG_\(MACH_SUN.I\)=./\1/p' $i)
        echo "config TARGET_$TARGET"
        echo "	bool \"$TARGET\""
        echo "	depends on $MACH"
        echo
    done

defconfigs were updated with a sed script (t):
    # Extract board from first entry of CONFIG_SYS_EXTRA_OPTIONS,
    /^CONFIG_SYS_EXTRA_OPTIONS/ {
        s/^\(CONFIG_SYS_EXTRA_OPTIONS="\)\([^,"]\+\),\?\(.*\)/\1\3\nCONFIG_TARGET_\2=y/;

        # Print and delete first line (CONFIG_SYS_EXTRA_OPTIONS), leaving
        # CONFIG_TARGET_<BOARD> in pattern space
        P;D;
    };

    # Move CONFIG_TARGET_<BOARD> to hold space
    /^CONFIG_TARGET/{h;n}

    # Print CONFIG_TARGET_<BOARD> after CONFIG_MACH_<SOC> in either SPL or
    # normal mode.
    /^CONFIG_MACH/{p;g;p;n};
    /^\+S:CONFIG_MACH/{p;g;s/^CONFIG_TARGET/+S:&/;p;n};

    # Print any remaining lines normally
    p;
Run as:
    sed -i -n -f t $(git grep -l CONFIG_ARCH_SUNXI configs/*)
and then manually removing the one instance of CONFIG_SYS_EXTRA_OPTIONS="" from
Colombus_defconfig

board/sunxi/Makefile was updated with:
    sed -e 's/^\(obj-\$(CONFIG_\)\(.*\)\().*+= dram_.*\)/\1TARGET_\2\3/g' board/sunxi/Makefile
and manually retabbing a few lines to line up again.

The board descriptions could certainly be improved.

Signed-off-by: Ian Campbell <ijc@hellion.org.uk>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
diff --git a/configs/Cubieboard_defconfig b/configs/Cubieboard_defconfig
index 9152b25..0bc45fd 100644
--- a/configs/Cubieboard_defconfig
+++ b/configs/Cubieboard_defconfig
@@ -1,6 +1,7 @@
 CONFIG_SPL=y
-CONFIG_SYS_EXTRA_OPTIONS="CUBIEBOARD,AXP209_POWER,SUNXI_EMAC,AHCI,SATAPWR=SUNXI_GPB(8),USB_EHCI"
+CONFIG_SYS_EXTRA_OPTIONS="AXP209_POWER,SUNXI_EMAC,AHCI,SATAPWR=SUNXI_GPB(8),USB_EHCI"
 CONFIG_FDTFILE="sun4i-a10-cubieboard.dtb"
 +S:CONFIG_ARM=y
 +S:CONFIG_ARCH_SUNXI=y
 +S:CONFIG_MACH_SUN4I=y
++S:CONFIG_TARGET_CUBIEBOARD=y