Now that those common Allwinner config symbols are defined automatically
for all boards in their Kconfig files, we can remove the now redundant
definitions from the boards' _defconfig files.

Some boards had a differing definiton for some of those symbols, it
looks like mostly to "merge races" when the symbol was introduced (new
board *_defconfig file missed the "add symbol to all files" patch).

Signed-off-by: Andre Przywara
Acked-by: Maxime Ripard
Tested-by: Jagan Teki # Amarula A64-Relic
Reviewed-by: Jagan Teki