staging: net: netlogic: Remove unneeded cast

Fix Coccinelle alert:

drivers/staging//netlogic/xlr_net.c:996:12-30: WARNING: casting value returned by memory allocation function to (struct xlr_adapter *) is useless.

This issue was detected by using the Coccinelle software.

Signed-off-by: Christopher Diaz Riveros <chrisadr@gentoo.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>