staging: wfx: correctly cast data on big-endian targets

When built for a big-endian target, original code caused error:

    include/uapi/linux/swab.h:242:29: note: expected '__u32 * {aka unsigned int *}' but argument is of type 'struct hif_mib_protected_mgmt_policy *'

Fixes: f95a29d4 ("staging: wfx: add HIF commands helpers")
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jérôme Pouiller <jerome.pouiller@silabs.com>
Link: https://lore.kernel.org/r/20191008094232.10014-5-Jerome.Pouiller@silabs.com


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