msm: mdss: move dcs-cmd-by-left out of partial update

dcs-cmd-by-left flag can be set without partial update being
enabled. Therefore remove partial update checking during
parsing dcs-cmd-by-left.

CRs-Fixed: 698733
Change-Id: I3e81ecc95e80a2d2bc970d8d9350cfc7736d1a29
Signed-off-by: Kuogee Hsieh <khsieh@codeaurora.org>