disp: msm: sde: fix rm/kms for handling all cont-splash cases

Fix resource and splash buffer handling in resource manager
and sde_kms to support continuous splash to be enabled/disabled
independently in multiple built-in display usecase.

Change-Id: I446ea9b08a794e2b053c37f55b31e51404bbcf71
Signed-off-by: Veera Sundaram Sankaran <veeras@codeaurora.org>