haswell: Factor out max_ddr3_freq

All mainboards choose the maximum speed of DDR3-1600.

Change-Id: I8863f9d1df950b924f596689ebf1bfda5d317e06
Signed-off-by: Angel Pons <th3fanbus@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/43120
Reviewed-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-by: Tristan Corrick <tristan@corrick.kiwi>
Reviewed-by: Michael Niewöhner
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/intel/baskingridge/romstage.c

@@ -52,7 +52,6 @@ void mainboard_fill_pei_data(struct pei_data *pei_data)
 	pei_data->spd_addresses[2] = 0xa4;
 	pei_data->spd_addresses[3] = 0xa6;
 	pei_data->ec_present = 0;
-	pei_data->max_ddr3_freq = 1600;
 
 	struct usb2_port_setting usb2_ports[MAX_USB2_PORTS] = {
 		/* Length, Enable, OCn#, Location */