drm/msm/dp: delete unnecessary debugfs error handling

drm/msm/dp: delete unnecessary debugfs error handling

Currently the error checking logic in the dp_debug module could
pass zero to PTR_ERR and it causes the below kbot warnings:

drivers/gpu/drm/msm/dp/dp_debug.c:378 dp_debug_init()
warn: passing zero to 'PTR_ERR'
drivers/gpu/drm/msm/dp/dp_debug.c:387 dp_debug_init()
warn: passing zero to 'PTR_ERR'
drivers/gpu/drm/msm/dp/dp_debug.c:396 dp_debug_init()
warn: passing zero to 'PTR_ERR'
drivers/gpu/drm/msm/dp/dp_debug.c:405 dp_debug_init()
warn: passing zero to 'PTR_ERR'

Debugfs functions are not supposed to be checked in the normal
case so delete this code.  Also it silences the above Smatch
warnings that we're checking for NULL when these functions only
return error pointers.

Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Link: https://lore.kernel.org/r/1614971839-2686-3-git-send-email-abhinavk@codeaurora.org
Signed-off-by: Rob Clark <robdclark@chromium.org>