Add compatible string to schgm-flash DT node. This was removed from the bulk DT porting for Ravelin on qcom-6.6 device-tree branch. Change-Id: I16d410ce8cc15278b0d8a3480a1e7fd5a044669f Signed-off-by: Shilpa Suresh <quic_c_sbsure@quicinc.com>