wifi: mwifiex: fix endian annotations in casts

These cause sparse warnings, and since the device generally
works in little endian we can assume the code is correct, so
just fix the casts accordingly. No binary changes on x86.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Brian Norris <briannorris@chromium.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220904212910.3f72609a3825.If4048592701bf04981be1dab18eaaa339b2ea382@changeid