nfc: port100: constify protocol list array

File-scope "port100_protocol" array is read-only and passed as pointer
to const, so it can be made a const to increase code safety.

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