msm: acpuclock-8k: Return error on unexpected CPU_UP_PREPARE

If a CPU has never been brought up before acpuclock initializes
we may NULL pointer dereference when trying to access per-CPU
resources. Deny the CPU from coming online if it didn't come up
before acpuclock initialized since the code isn't prepared to
handle such a case.

Change-Id: Iddbc326e347b0d0c2d799e003c1d82b4884d7247
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>