mb/google/fatcat/var/francka: Override DRAM Freq

Due to the hardware limitation on francka, reduce the memory speed to
7467 MT/s.

BUG=b:373394046
TEST=emerge-fatcat coreboot

Change-Id: I9c45c90952e20fc96943df03f591075338624e88
Signed-off-by: Subrata Banik <subratabanik@google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/85102
Reviewed-by: Dtrain Hsu <dtrain_hsu@compal.corp-partner.google.com>
Reviewed-by: Amanda Hwang <amanda_hwang@compal.corp-partner.google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <ericllai@google.com>

src/mainboard/google/fatcat/variants/francka/overridetree.cb

@@ -1,5 +1,7 @@
 chip soc/intel/pantherlake
 
+	register "max_dram_speed_mts" = "7467"
+
 	device domain 0 on
 	end
 end