drivers/sbus/char/envctrl.c: ignore orderly_poweroff return value

orderly_poweroff() unconditionally returns 0, so remove the dead code that
checks the return value.

A future patch will change the return type to void.

Signed-off-by: Joel Stanley <joel@jms.id.au>
Acked-by: David S. Miller <davem@davemloft.net>
Cc: Fabian Frederick <fabf@skynet.be>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Jeremy Kerr <jk@ozlabs.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>