aspeed/scu: Add AST2700 support

aspeed/scu: Add AST2700 support

AST2700 have two SCU controllers which are SCU and SCUIO.
Both SCU and SCUIO registers are not compatible previous SOCs
, introduces new registers and adds ast2700 scu, sucio class init handler.

The pclk divider selection of SCUIO is defined in SCUIO280[20:18] and
the pclk divider selection of SCU is defined in SCU280[25:23].
Both of them are not compatible AST2600 SOCs, adds a get_apb_freq function
and trace-event for AST2700 SCU and SCUIO.

Signed-off-by: Troy Lee <troy_lee@aspeedtech.com>
Signed-off-by: Jamin Lin <jamin_lin@aspeedtech.com>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
[clg: Fixed spelling : Unhandeled -> Unhandled ]