drm/msm/dsi-staging: avoid ctl soft reset when cont-splash is enabled

Avoid resetting the dsi ctrl when continuous splash screen is
enabled as it might cause flicker during the transition from
UEFI to kernel.

Change-Id: I0f9a28867fb83c26d39a2212916273cd686d7d23
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>