nfc: nfcsim: constify drvdata (struct nfcsim)

nfcsim_abort_cmd() does not modify struct nfcsim, so local variable
can be a pointer to const.

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