arm64: dts: qcom: ipq6018: fix usb reference period

Reference clock period for rate of 24MHz is 41ns (0x29).

Link: https://lore.kernel.org/r/1965fc315525b8ab26cf9f71f939c24d@codeaurora.org
Link: https://lore.kernel.org/r/a1932eba-564c-fe32-f220-53aa75250105@seco.com
Fixes: 20bb9e3d

 ("arm64: dts: qcom: ipq6018: add usb3 DT description")
Reported-by: Kathiravan T <kathirav@codeaurora.org>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/4f4df55cf44cd0fd7d773aca171d4f48662fb1a5.1642704221.git.baruch@tkos.co.il