wifi: cw1200: use get_unaligned_le64()

Instead of the code here that copies into a variable
first and then flips endianness, which confuses sparse,
just directly use get_unaligned_le64().

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220904212910.a5c9ea122f0f.If786a66f8fd9d45659cd5a2532cf395e21334453@changeid