As soon as device boots up, there are few test cases like boot KPIs
which rely on dmesg, but by the time these tests are run on Sun,
buffer is getting overwritten and test cases were failing.
To unblock the tests, increase buffer size to 512K from 256K.
Change-Id: Ie6a810297553d1a104d00f87dae3bff51dac7b95
Signed-off-by: Satya Durga Srinivasu Prabhala <quic_satyap@quicinc.com>