[ARM] 3921/1: S3C24XX: remove bast_defconfig

Remove the bast_defconfig, as it has not been updated
since 2.6.13. The s3c2410_defconfig should be a good
replacement.
Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>