iwl3945: remove obsolete irq handling

3945 hardware does not emit the interrupts CSR_INT_BIT_RF_KILL (rfkill
toggled) and CSR_INT_BIT_CT_KILL (adapter too hot). Hence this part of code
can be removed since iwl3945_irq_tasklet does not handle 4965 hw at all.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>