aspeed/smc: rework the prototype of the AspeedSMCFlash helper routines

Change the routines prototype to use a 'AspeedSMCFlash *' instead of
'AspeedSMCState *'. The result will help in making future changes
clearer.

Also change aspeed_smc_update_cs() which uselessly loops on all slave
devices to update their status.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Andrew Jeffery <andrew@aj.id.au>
Message-id: 1483979087-32663-4-git-send-email-clg@kaod.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
