brcmfmac: Fix incorrect type assignments for keep-alive

cpu_to_le16 has been used for all keep-alive fields, but 'perdio_msec'
is a 32-bit field and 'keep_alive_id' a 8-bit one. Fix that.

Fixes: 7a6cfe28 ("brcmfmac: Configure keep-alive packet on suspend")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Loic Poulain <loic.poulain@linaro.org>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/1638953708-29192-1-git-send-email-loic.poulain@linaro.org