sunxi: Add default environment size

On boards that defines ENV_IS_NOWHERE, such as the NES classic, commit
19dbe7d1a3f7 ("common: Move environment choice to Kconfig") broke the build
because of a missing environment size.

Reintroduce a default environment size consistent with what we had before.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
1 file changed