msm: mdss: clear solid fill pipe b/w vote

solid fill pipe b/w vote is not reset properly. This causes
a mismatch wrt the bw calculation in sdm and results in a bw
validation check failure.

Change-Id: Ie4f36c376efe3eb405cf4aca6f2ed79ee9849950
Signed-off-by: Naseer Ahmed <naseer@codeaurora.org>