NFC: Fix missing static declarations

This patch fixes 3 sparse warnings:
nfcsim.c:63:25: sparse: symbol 'wq' was not declared.
nfcsim.c:484:12: sparse: symbol 'nfcsim_init' was not declared.
nfcsim.c:525:13: sparse: symbol 'nfcsim_exit' was not declared.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Thierry Escande <thierry.escande@linux.intel.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>