dt-bindings: arm: qcom: Add compatible for oneplus,billie2 phone

oneplus,billie2 (OnePlus Nord N100) is based on QualComm Snapdragon
SM4250 SoC.

Add support for the same in dt-bindings.

Signed-off-by: Iskren Chernev <iskren.chernev@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Caleb Connolly <caleb@connolly.tech>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220919180618.1840194-4-iskren.chernev@gmail.com