kfifo: add kfifo_dma_out_prepare_mapped()

When the kfifo buffer is already dma-mapped, one cannot use the kfifo
API to fill in an SG list.

Add kfifo_dma_in_prepare_mapped() which allows exactly this. A mapped
dma_addr_t is passed and it is filled into provided sgl too. Including
the dma_len.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Cc: Stefani Seibold <stefani@seibold.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20240405060826.2521-8-jirislaby@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>