scatterlist: move the NEED_SG_DMA_LENGTH config symbol to lib/Kconfig

This way we have one central definition of it, and user can select it as
needed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
16 files changed