mwifiex: re-fix for unaligned accesses

A patch from 2017 changed some accesses to DMA memory to use
get_unaligned_le32() and similar interfaces, to avoid problems
with doing unaligned accesson uncached memory.

However, the change in the mwifiex_pcie_alloc_sleep_cookie_buf()
function ended up changing the size of the access instead,
as it operates on a pointer to u8.

Change this function back to actually access the entire 32 bits.
Note that the pointer is aligned by definition because it came
from dma_alloc_coherent().

Fixes: 92c70a95

 ("mwifiex: fix for unaligned reads")
Acked-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>