rtl8150: rtl8150_disconnect(...) does not need tasklet_disable(...)

Executing cmd 'rmmod rtl8150' does not return(if your device connects
to host), the root cause is tasklet_disable() causes tasklet_kill()
block, remove it from rtl8150_disconnect().

Signed-off-by: Huajun Li <huajun.li.lee@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>