msm: mdss: fix race condition between shutdown thread and fb ioctl

Currently all entires into fb driver are synchronized with shutdown
context except fb ioctl context. fb ioctl is an asynchronous entry to
fb driver which can be called simultaneously from two different user
processes. Synchronize these fb ioctls and shutdown context to prevent
race condition.

Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
msm: mdss: fb: null check mfd data

Add appropriate null check for mfd data structure
before accessing it's members. This prevents null
pointer accesses in the driver.

Signed-off-by: Manoj Rao <manojraj@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
msm: mdss: Add error handling in mdss_fb_no_update_notify_timer_cb

Return in case mfd is NULL to avoid NULL pointer dereference.

Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>