[Arista] Fix flash size computation for Lodoga (#8622)

The Lodoga platform also matched crow which was hardcoding the flash
size to 3700. This change enables autodetect on Clearlake which in turns
allows autodetect for Lodoga.

The threshold was bumped from 3700 to 4000 because size computation can
differ slightly and report slightly above 3700.

files/Aboot/boot0.j2

@@ -477,7 +477,6 @@ write_platform_specific_cmdline() {
     if [ "$platform" = "crow" ]; then
         # Assuming sid=Clearlake
         aboot_machine=arista_7050_qx32s
-        flash_size=3700
         cmdline_add modprobe.blacklist=radeon,sp5100_tco
     fi
     if [ "$sid" = "Upperlake" ] || [ "$sid" = "UpperlakeES" ]; then
@@ -591,7 +590,7 @@ write_platform_specific_cmdline() {
 
     if [ $flash_size -ge 28000 ]; then
         varlog_size=4096
-    elif [ $flash_size -gt 3700 ]; then
+    elif [ $flash_size -gt 4000 ]; then
         varlog_size=400
     else
         varlog_size=256