ARM: dts: msm: Rename L2, CCI clock gating mode to wfi for MSM8994

The clock gating spm command and lpm mode were referred to as retention
in L2, CCI spm and lpm nodes. This results in q2s being configured for
retention when l2 and cci spm's are programmed for clock gating. Fix
this by renaming clock gating mode to wfi.

Change-Id: I6a14b9f8b4b3bda498761b298812b7b7a026f13e
Signed-off-by: Karthik Parsha <kparsha@codeaurora.org>