MSIM: Change default fallback subId value

Some times getPhoneId(DEFAULT_SUBSCRIPTION_ID) returning
INVALID_PHONE_INDEX which causing some error application layer.

Change mDefaultFallbackSubId default value to DUMMY_SUB_ID_BASE,
with this change getPhoneId() always returns phone Id as '0' for all
valid subIds.

Change DUMMY_SUB_ID_BASE range.

Change-Id: If5ac1b830fefcd7cbb043261e231677db8ba6951