drivers/misc: ignore minimum encryption level change for stream type 1

If the HDCP repeater is already authenticated with a stream type 1
ignore subsequent writes to change minimum encryption level.

This shall ensure that there are no transitions to other encryption
levels in the middle of a secure playback and thus avoid any
visual artifacts in case of re-authentication.

Change-Id: I8496c0a82101df4dcc5234e2afd5a2fe11a5eabd
Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>