serial: msm-geni: Use upstream Linux bindings

The name "se" is used in upstream Linux device trees and has been for
ages, long before this U-Boot-ism was introduced. Same goes for the
existing compatible. Get rid of that.

[vzapolskiy: removed a ready change in the driver]
Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>