usb: avoid warnings for unused pm functions

[Arnd Bergmann]

This series addresses a couple of similar warnings in USB
host and phy drivers. In each case, there is a mismatch between
the references to some functions and the #ifdef hiding those
functions (if any).

The series gets rid of all those #ifdes and instead changes
the drivers that don't already get it wrong to annotate
the functions as __maybe_unused. However, I am not changing
any files that consistently get the #ifdefs right.

	Arnd

[PATCH 1/6] usb: host: unhide suspend/resume declarations
[PATCH 2/6] usb: xhci-mtk: use __maybe_unused to hide pm functions
[PATCH 3/6] usb: ohci-at91: use __maybe_unused to hide pm functions
[PATCH 4/6] usb: ehci-atmel: use __maybe_unused to hide pm functions
[PATCH 5/6] phy: dm816x: use __maybe_unused to hide pm functions
[PATCH 6/6] phy: twl4030: use __maybe_unused to hide pm functions