nfc: fdp: use unsigned int as loop iterator

Loop iterators are simple integers, no point to optimize the size and
use u8.  It only raises the question whether the variable is used in
some other context.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>