[ARM] GTA02: build fixes (s3c2410_nand_set usage)

This patch fixes two errors we get when building GTA02 kernel.

~ use_bbt is incorrect, we need flash_bbt.

~ We do not need .force_soft_ecc because we can unset
  CONFIG_MTD_NAND_S3C2410_HWECC.

Signed-off-by: Nelson Castillo <arhuaco@freaks-unidos.net>
[ben-linux@fluff.org: updated patch description]
Signed-off-by: Ben Dooks <ben-linux@fluff.org>