iwlwifi: avoid firmware command sending if rfkill is enabled

This patch fixed a ucode timeout issue and worked code with suspend
to disk.

Signed-off-by: Mohamed Abbas <mabbas@linux.intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>