drm/msm: correct iteration for old crtc in sde kms

In 4.19, the use of for_each_crtc is deprecated and replaced
with each old and/or new crtc. Previously, commit e1905eb4
("drm/msm: snapshot of drm msm display and drm from 4.14 to 4.19")
used old crtcs to replace the loop in secure transition. This
change corrects the loop to iterate over new crtcs.

Change-Id: Ief0d061a4d190ee5b018593e7979f055351bd484
Signed-off-by: Samantha Tran <samtran@codeaurora.org>