This Kconfig entry should declare a dependency on OF

Fixes: 67b27dbe ("phy: qualcomm: Add Synopsys 28nm Hi-Speed USB PHY driver")
Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://lore.kernel.org/r/20201113151225.1657600-3-bryan.odonoghue@linaro.orgSigned-off-by: Vinod Koul <vkoul@kernel.org>