disp: msm: sde: cleanup ctl/intf registers on cmd encoder disable

The SDE RM determines the number of displays enabled in cont-splash by
checking the INTF_ACTIVE bits in the ctl. The trusted-vm relies on the
same cont-splash path during transitions and the stale ctl INTF_ACTIVE
on dual display usecases leads to wrong status check. Currently, only
video/wb encoders use the phys_encoder disable helper during encoder
disable to clear out few ctl/intf registers. Extend it for cmd encoder
as well to remove the stale entries.

Change-Id: I7f21ef46178ce3943ee85abdf29f7cdef93d7c52
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>