Vlv2TbltDevicePkg/PpmPolicy: Remove the unused variable

Vlv2TbltDevicePkg/PpmPolicy: Remove the unused variable

Fix the following error from gcc:

Vlv2TbltDevicePkg/PpmPolicy/PpmPolicy.c: In function ?PpmPolicyEntry?:
Vlv2TbltDevicePkg/PpmPolicy/PpmPolicy.c:50:29: error: variable ?MaxRatio? set but not used [-Werror=unused-but-set-variable]

Cc: David Wei <david.wei@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>