sfc: Don't specify unexistent IRQ

Neither the lm90 driver nor the lm87 driver do support interrupts, so
there is no point in specifying one when declaring the devices.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>