usb: dwc3-msm: Fix compile error when CONFIG_PM_* undefined

The SET_SYSTEM_SLEEP_PM_OPS and SET_RUNTIME_PM_OPS macros only
assign the PM functions if CONFIG_PM_SLEEP and CONFIG_PM_RUNTIME,
respectively, are defined. Otherwise the compiler warns about
unreferenced functions. Wrap the function definitions with the
appropriate #ifdefs.

Change-Id: I79f3d3b8615de435d1f3bbcc2925ce6b67fb1239
Signed-off-by: Jack Pham <jackp@codeaurora.org>