mei: iamthif: remove useless iamthif_ioctl variable

iamthif_ioctl is obsolete and can be safely dropped
Currently it is set to true during driver runtime

Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>