Use hid_get_data_unsigned() instead of hid_get_data() when reading the
key-codes from the USB keyboard. Negative key-codes are currently skipped.

While at it use the bit size value provided by the HID location structure
instead of assuming a value of 8.

This fixes a regression issue after r357861.

Reported by: Minoru TANABE <kotanabe3@gmail.com>
PR: 224592
PR: 233884
MFC after: 3 days
Sponsored by: Mellanox Technologies