msm: mdss: prevent excessive logging after shutdown requested

Current frame-buffer driver gets shutdown call back and it turns the
display off. Once shutdown call-back is received, any subsequent
frame-buffer opens are rejected and an error log is generated. Now
user-land display clients are not aware of shutdown and they keep
opening the frame-buffer devices repeatedly ignoring the failures and
notifications sent by the driver. Due to this, excessive logging is
observed which in turn leads to watch-dog bite and a crash. Prevent
this by generating error log only once and keep sending sysfs
notification for every rejected frame-buffer open.

Change-Id: I9df6cb708a2d6c986a31324540a3d040dffbcdfc
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>