phy: USB_LGM_PHY should depend on X86

The Intel Lightning Mountain (LGM) USB3 USB is only present on Intel
Lightning Mountain SoCs. Hence add a dependency on X86, to prevent
asking the user about this driver when configuring a kernel without
Intel Lightning Mountain platform support.

Fixes: 1cce8f73a561c944 ("phy: Add USB3 PHY support for Intel LGM SoC")
Signed-off-by: Geert Uytterhoeven <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Vinod Koul <[e-mail]>

drivers/phy/Kconfig

···
 config USB_LGM_PHY
 	tristate "INTEL Lightning Mountain USB PHY Driver"
 	depends on USB_SUPPORT
+	depends on X86 || COMPILE_TEST
 	select USB_PHY
 	select REGULATOR
 	select REGULATOR_FIXED_VOLTAGE