staging: qlge: Factor out duplicated expression

Given that (u16) 65536 == 0, that expression can be replaced by a simple
cast.

Signed-off-by: Benjamin Poirier <bpoirier@suse.com>
Link: https://lore.kernel.org/r/20190927101210.23856-12-bpoirier@suse.com


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