msm: mdss: dsi: fix slab-out-of-bounds issue

While handling dsi_gen_read_status, status buffer
was xlogging without checking for its max size.
Add proper conditional check to xlog status buffer.

Change-Id: Ia5a1fe18de123d2911c31ae79492b96f67e1273d
Signed-off-by: Narender Ankam <nankam@codeaurora.org>