sunxi: Drop FEL variants of defconfigs.

This can now be configured via Kconfig, e.g. with:

    $ make BOARD_defconfig
    $ echo CONFIG_SPL_FEL=y >> .config
    $ echo CONFIG_SPL_FEL=y >> spl/.config

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>

configs/Cubieboard2_FEL_defconfig

-CONFIG_SPL=y
-+S:CONFIG_SPL_FEL=y
-CONFIG_SYS_EXTRA_OPTIONS="CUBIEBOARD2,AXP209_POWER,SUNXI_GMAC,AHCI,SATAPWR=SUNXI_GPB(8),USB_EHCI"
-CONFIG_FDTFILE="sun7i-a20-cubieboard2.dtb"
-+S:CONFIG_ARM=y
-+S:CONFIG_ARCH_SUNXI=y
-+S:CONFIG_MACH_SUN7I=y

configs/Cubietruck_FEL_defconfig

-CONFIG_SPL=y
-+S:CONFIG_SPL_FEL=y
-CONFIG_SYS_EXTRA_OPTIONS="CUBIETRUCK,AXP209_POWER,SUNXI_GMAC,RGMII,AHCI,SATAPWR=SUNXI_GPH(12),USB_EHCI"
-CONFIG_FDTFILE="sun7i-a20-cubietruck.dtb"
-+S:CONFIG_ARM=y
-+S:CONFIG_ARCH_SUNXI=y
-+S:CONFIG_MACH_SUN7I=y