sunxi: reorganize mctl_mem_matches_* functions

mctl_mem_matches and mctl_mem_matches_base identical functions. To
avoid code duplication move them to dram_helpers and make
mctl_mem_matches use generic mctl_mem_matches_base.

Signed-off-by: Andrey Skvortsov <andrej.skvortzov@gmail.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>