clk: qcom: gcc-sc8280xp: use retention for USB power domains

Since commit d3997239 ("clk: qcom: gdsc: Fix the handling of
PWRSTS_RET support) retention mode can be used on sc8280xp to maintain
state during suspend instead of leaving the domain always on.

This is needed to eventually allow the parent CX domain to be powered
down during suspend.

Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20220929161124.18138-1-johan+linaro@kernel.org