HID: surface-hid: Fix integer endian conversion

We want to convert from 16 bit (unsigned) little endian values contained
in a packed struct to CPU native endian values here, not the other way
around. So replace cpu_to_le16() with get_unaligned_le16(), using the
latter instead of le16_to_cpu() to acknowledge that we are reading from
a packed struct.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: b05ff100

 ("HID: Add support for Surface Aggregator Module HID transport")
Signed-off-by: Maximilian Luz <luzmaximilian@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>