PCI: qcom: Add ddrss_sf_tbu flag

Qualcomm PCIe driver uses compatible string to check if the ddrss_sf_tbu
clock should be used. Since sc7280 support has added flags, switch to
the new mechanism to check if this clock should be used.

Link: https://lore.kernel.org/r/20220223101435.447839-4-dmitry.baryshkov@linaro.org


Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Acked-by: Stanimir Varbanov <svarbanov@mm-sol.com>