phy: realtek: Realtek PHYs should depend on ARCH_REALTEK

The Realtek SoC USB2 and USB3 PHY Transceivers are only present on
Realtek Digital Home Center (DHC) RTD series SoCs.  Hence add a
dependency on ARCH_REALTEK, to prevent asking the user about these
drivers when configuring a kernel without Realtek SoC support.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/2892527cac9af6fa8f5e7b8daeffd7d4351fde68.1692113167.git.geert+renesas@glider.be


Signed-off-by: Vinod Koul <vkoul@kernel.org>