test-qemu: Use romulus instead of witherspoon for AST2500

Witherspoon's UBI support seems to be broken. However, Romulus is also
used by CI as a smoke test, so it makes sense to check that anyway.

Change-Id: I4c20f1e800b43ff5614cb34388149657529a5130
Signed-off-by: Andrew Jeffery <andrew@codeconstruct.com.au>
1 file changed