sunxi: icnova-a20-swac_defconfig: Remove CMD_BMP from

This configuration is not necessary in a defconfig file so
it is removed from the SYS_EXTRA_OPTIONS.

Signed-off-by: Mylène Josserand <mylene.josserand@free-electrons.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>