Vlv2TbltDevicePkg/PlatformInitPei: Suppress the gcc error message

Vlv2TbltDevicePkg/PlatformInitPei: Suppress the gcc error message

Fix the following error from gcc:

Vlv2TbltDevicePkg/PlatformInitPei/PlatformEarlyInit.c: In function 'GetWakeupEventAndSaveToHob':
Vlv2TbltDevicePkg/PlatformInitPei/PlatformEarlyInit.c:147:11: error: variable 'WakeEventData' set but not used [-Werror=unused-but-set-variable]

Although the function name is "GetWakeupEventAndSaveToHob",
WakeEventData was never really used or passed to any other function.
Given the fact that the function is served as an example, it'd better to
keep the code related to WakeEventData. Just add a debug statement to
suppress the error message.

Cc: David Wei <david.wei@intel.com>
Cc: "Wu, Hao A" <hao.a.wu@intel.com>
Cc: "Lu, ShifeiX A" <shifeix.a.lu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: David Wei <david.wei@intel.com>