aspeed/smc: remove call to aspeed_smc_update_cs() in reset function

Instead, we can simply set the irq level when unselecting the slave
devices. This change prepares ground for a subsequent cleanup of the
aspeed_smc_update_cs() routine which uselessly loops on all slaves to
update their status.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Message-id: 1483979087-32663-3-git-send-email-clg@kaod.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>