labs: kernel-dma: Remove trailing parenthesis from kfunc name

the \kfunc macro doesn't like having the trailing () in a function name,
it adds them automatically. Adding the () actually produces a broken
link.

Signed-off-by: Maxime Chevallier <[email protected]>

labs/kernel-serial-dma/kernel-serial-dma.tex

@@ -65,7 +65,7 @@ \section{Prepare the DMA controller}
 channel properties and their names. While uart2 seem to be connected to
 the DMA controller through two different channels (one for each
 direction), uart4 is not. Hence, when requesting the channels with
-\kfunc{dma_request_chan()}, we must take care to check and return the error code
+\kfunc{dma_request_chan}, we must take care to check and return the error code
 wrapped in the returned \kstruct{dma_chan} pointer. This can be done with the
 \code{IS_ERR()} and \code{PTR_ERR()} macros. You may display the corresponding
 error string with {\tt \%pe}! Also make sure that this case is correctly handled