note tahan, morgan800cc as a BMC-lite

Summary:
Otherwise we will accidentally start the watchdog and reset while wiping the
second chip:

https://www.internalfb.com/intern/provisioning/asset_details/911771887375906

XXX This needs to be table driven off platforms.thrift.

Test Plan:
```
0 ~/local/openbmc/tools/flashy $ ./build.sh && ./build_dev.sh && go test ./... && echo it works
ok      github.com/facebook/openbmc/tools/flashy        (cached)
ok      github.com/facebook/openbmc/tools/flashy/checks_and_remediations/bletchley      0.006s
?       github.com/facebook/openbmc/tools/flashy/flash_procedure        [no test files]
?       github.com/facebook/openbmc/tools/flashy/lib/logger     [no test files]
ok      github.com/facebook/openbmc/tools/flashy/checks_and_remediations/common (cached)
ok      github.com/facebook/openbmc/tools/flashy/checks_and_remediations/galaxy100      (cached)
ok      github.com/facebook/openbmc/tools/flashy/checks_and_remediations/grandteton     (cached)
ok      github.com/facebook/openbmc/tools/flashy/checks_and_remediations/wedge100       (cached)
ok      github.com/facebook/openbmc/tools/flashy/checks_and_remediations/yamp   (cached)
ok      github.com/facebook/openbmc/tools/flashy/install        (cached)
?       github.com/facebook/openbmc/tools/flashy/tests  [no test files]
?       github.com/facebook/openbmc/tools/flashy/utilities      [no test files]
ok      github.com/facebook/openbmc/tools/flashy/lib/fileutils  0.010s
ok      github.com/facebook/openbmc/tools/flashy/lib/flash      (cached)
ok      github.com/facebook/openbmc/tools/flashy/lib/flash/flashcp      (cached)
ok      github.com/facebook/openbmc/tools/flashy/lib/flash/flashutils   0.006s
ok      github.com/facebook/openbmc/tools/flashy/lib/flash/flashutils/devices   (cached)
ok      github.com/facebook/openbmc/tools/flashy/lib/step       (cached)
ok      github.com/facebook/openbmc/tools/flashy/lib/utils      0.441s
ok      github.com/facebook/openbmc/tools/flashy/lib/validate   0.007s
ok      github.com/facebook/openbmc/tools/flashy/lib/validate/image     (cached)
ok      github.com/facebook/openbmc/tools/flashy/lib/validate/partition 0.017s
it works
0 ~/local/openbmc/tools/flashy $
```

Reviewed By: gepoggio

Differential Revision: D59759896

fbshipit-source-id: b5c742f8370dc5f79da403d41be3c096b534ca0e

tools/flashy/lib/utils/system.go

@@ -368,7 +368,7 @@ var IsLFOpenBMC = func() (bool) {
 // IsBMCLite check whether the system is running BMC-lite
 // For S368275.   Make this beautiful later.
 var IsBMCLite = func() (bool) {
-	magics := []string{"fbdarwin", "meru", "janga", "montblanc"}
+	magics := []string{"fbdarwin", "meru", "janga", "montblanc", "tahan", "morgan800cc"}
 
 	issueBuf, err := fileutils.ReadFile(etcIssueFilePath)
 	if err != nil {