palmetto-bmc: Configure the SCU's hardware strapping register

palmetto-bmc: Configure the SCU's hardware strapping register

The magic constant configures the following options:

* 28:27: Configure DRAM size as 256MB
* 26:24: DDR3 SDRAM with CL = 6, CWL = 5
* 23: Configure 24/48MHz CLKIN
* 22: Disable GPIOE pass-through mode
* 21: Disable GPIOD pass-through mode
* 20: Enable LPC decode of SuperIO 0x2E/0x4E addresses
* 19: Disable ACPI
* 18: Configure 48MHz CLKIN
* 17: Disable BMC 2nd boot watchdog timer
* 16: Decode SuperIO address 0x2E
* 15: VGA Class Code
* 14: Enable LPC dedicated reset pin
* 13:12: Enable SPI Master and SPI Slave to AHB Bridge
* 11:10: Select CPU:AHB ratio = 2:1
* 9:8: Select 384MHz H-PLL
* 7: Configure MAC#2 for RMII/NCSI
* 6: Configure MAC#1 for RMII/NCSI
* 5: No VGA BIOS ROM
* 4: Boot using 32bit SPI address mode
* 3:2: Select 16MB VGA memory
* 1:0: Boot from SPI flash memory

Signed-off-by: Andrew Jeffery <[email protected]>
Reviewed-by: Cédric Le Goater <[email protected]>
Reviewed-by: Peter Maydell <[email protected]>
Tested-by: Cédric Le Goater <[email protected]>
Message-id: 1466744305[email protected]
Signed-off-by: Peter Maydell <[email protected]>