msm: mdss: remove extra copy_from_user in wb path

An extra copy_to_user is done on the output_layer
buffer in writeback path before using it. This leads
to error in copy_from_user as the source buffer is
a buffer allocated in kernel space. Remove the
extra copy_from_user call.

Change-Id: Icec8c60b7ef36e656786c62006a229b906cc8eaa
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>