msm: vidc: set ctrl to request sequence header for encoder

The encoder depended on a debug variable i.e. ftb_count, to
request firmware to send sequence header. Remove this
dependency and make the request only when the encoder
client requests using the provided set ctrl.

b/11051201

Change-Id: Iac4104c33eef62da553066c736b7adc87834d2ac
Signed-off-by: Arun Menon <avmenon@codeaurora.org>