sunxi: Drop qt840a_defconfig

The qt840a is one of the many tv-boxes using the "i12" A20 pcb, but it
populates only one of the 2 places for a 16 bit dram ic, thus reducing
the buswidth to 16 bits, and the amount of ram to 512M, which is why we
had a separate config for it.

This commit switches the generic i12-tvbox_defconfig over to DRAM
autoconfiguration, so that it will work with the qt840a too, and drops the
qt840a specific config, like we've done with other memory-amount specific
configs before.

Tested on a generic i12-tvbox with 32 bit bus-width / 1G RAM, and on a
qt840a with 16 bit bus-width / 512M RAM.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Ian Campbell <ijc@hellion.org.uk>
diff --git a/board/sunxi/dram_sun5i_auto.c b/board/sunxi/dram_sun5i_auto.c
index a5965db..e86b08e 100644
--- a/board/sunxi/dram_sun5i_auto.c
+++ b/board/sunxi/dram_sun5i_auto.c
@@ -1,4 +1,4 @@
-/* this file is generated, don't edit it yourself */
+/* DRAM parameters for auto dram configuration on sun5i and sun7i */
 
 #include <common.h>
 #include <asm/arch/dram.h>