msm: mdss: Fix ARGC copy size from user

User cfg for ARGC gives varying number of rgb stages. Fixed ARGC config
to only copy data based on number of RGB stages.

Change-Id: I425527b12364b03bbcd8c9d984a2675cd8444d62
Signed-off-by: Benet Clark <benetc@codeaurora.org>
Merge "msm: mdss: Fix ARGC copy size from user"