mb/google/octopus/var/fleex: Only check LTE sku on fleex

Fleex has other project share the same FW. Only fleex has LTE sku.
So we need to make sure it is fleex then check if LTE sku.

BUG=b:181946744
BRANCH=octopus
TEST=Check no SAR table can be loaded with sku id 4 and 5.

Signed-off-by: Eric Lai <ericr_lai@compal.corp-partner.google.com>
Change-Id: I9f3d5fed4315fc716acad1a07735221d154c377e
Reviewed-on: https://review.coreboot.org/c/coreboot/+/51288
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Marco Chen <marcochen@google.com>
Reviewed-by: Henry Sun <henrysun@google.com>

src/mainboard/google/octopus/variants/fleex/variant.c

@@ -7,10 +7,17 @@
 #include <soc/intel/apollolake/chip.h>
 
 #define MIN_LTE_SKU         4
+#define FLEEX_MAX_SKU         0x20
 
 static bool is_lte_sku(void)
 {
-	return (google_chromeec_get_board_sku() >= MIN_LTE_SKU);
+	uint32_t sku_id = google_chromeec_get_board_sku();
+
+	/* Only Fleex has LTE sku */
+	if (sku_id <= FLEEX_MAX_SKU)
+		return (sku_id >= MIN_LTE_SKU);
+
+	return false;
 }
 
 void variant_smi_sleep(u8 slp_typ)