mb/google/octopus: remove disable_periodic_retraining options

The Micron material that was broken has long since been fixed that
required this option. glkrvp had these stale entries and were
subsequently copied to octopus. Remove the need for this option.

BUG=b:35581751

Change-Id: Id73584367c2ad0e4958b5ea0f04a28e5fc82d085
Signed-off-by: Aaron Durbin <adurbin@chromium.org>
Reviewed-on: https://review.coreboot.org/27959
Reviewed-by: Paul Menzel <paulepanter@users.sourceforge.net>
Reviewed-by: Justin TerAvest <teravest@chromium.org>
Reviewed-by: Furquan Shaikh <furquan@google.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/mainboard/google/octopus/variants/baseboard/memory.c

@@ -96,7 +96,6 @@ static const struct lpddr4_sku skus[] = {
 		.ch0_dual_rank = 1,
 		.ch1_dual_rank = 1,
 		.part_num = "MT53B512M32D2NP",
-		.disable_periodic_retraining = 1,
 	},
 	/* MT53B256M32D1NP-062 WT:C - both logical channels */
 	[3] = {
@@ -104,7 +103,6 @@ static const struct lpddr4_sku skus[] = {
 		.ch0_rank_density = LP4_8Gb_DENSITY,
 		.ch1_rank_density = LP4_8Gb_DENSITY,
 		.part_num = "MT53B256M32D1NP",
-		.disable_periodic_retraining = 1,
 	},
 	/*
 	 * H9HCNNNBPUMLHR-NLE - both logical channels. While the parts