staging: r8188eu: remove unnecessary casting

The dhcpMessage struct member variable "cookie" is already declared
to be of type __be32. There is no need to cast it again as __be32.

Signed-off-by: Deepak R Varma <drv@mailo.com>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com> # Edimax N150
Link: https://lore.kernel.org/r/c333e22349c5c347c740b425330b35830b969fa9.1667755987.git.drv@mailo.com


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