ppc4xx: Update Katmai/44x_spd_ddr2.c code for optimal DDR2 setup

On Katmai the complete auto-calibration somehow doesn't seem to
produce the best results, meaning optimal values for RQFD/RFFD.
This was discovered by GDA using a high bandwidth scope,
analyzing the DDR2 signals. GDA provided a fixed value for RQFD,
so now on Katmai "only" RFFD is auto-calibrated.

This patch also adds RDCC calibration as mentioned on page 7 of
the AMCC PowerPC440SP/SPe DDR2 application note:
"DDR1/DDR2 Initialization Sequence and Dynamic Tuning"

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/include/configs/katmai.h b/include/configs/katmai.h
index 0aa4f2d..78c794a 100644
--- a/include/configs/katmai.h
+++ b/include/configs/katmai.h
@@ -111,6 +111,7 @@
 #define CONFIG_SPD_EEPROM	1	/* Use SPD EEPROM for setup	*/
 #define SPD_EEPROM_ADDRESS	{0x51, 0x52}	/* SPD i2c spd addresses*/
 #define CONFIG_DDR_ECC		1	/* with ECC support		*/
+#define CONFIG_DDR_RQDC_FIXED	0x80000038 /* optimal value found by GDA*/
 #undef  CONFIG_STRESS
 
 /*-----------------------------------------------------------------------