staging: comedi: Remove a newline inside a dereference

Remove a new line inside a dereference so that it is not on
multiple lines.
And avoid making the line go over 80 columns by moving the whole
dma_alloc_coherent() call back 4 columns. Problem found with
checkpatch.

Signed-off-by: Eisha Chen-yen-su <chenyensu0@gmail.com>
Acked-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>