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

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 <[email protected]>
Reviewed-by: Joel Stanley <[email protected]>
Reviewed-by: Andrew Jeffery <[email protected]>
Message-id: 1483979087[email protected]
Signed-off-by: Peter Maydell <[email protected]>