msm: kgsl: Remove legacy support for clock_set_flags

There are a few a3xx and a5xx targets that use the downstream API
clk_set_flags() for power control.  The bad news is that this is API is
not upstream, but the good news is that none of the targets that require
it are likely to be used in this kernel so we can safely keep most
of the target support and replace these calls with a WARN_ON mostly
as a nod to developers that might try to use this code as an example
for adding new target support later.

Change-Id: Ic0dedbad440b410d31a933891e436ea136bc796a
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>