disp: msm: allow DMS before cont-splash handoff

Currently dynamic mode-switch is allowed only after
the cont-splash handoff is handled during the first
frame. Remove this restriction for cmd-mode alone as
it can handle the use-case.

Change-Id: I5f9dc758f50a91fec0b9f710c74f2ea78c4e75eb
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>