disp: msm: sde: populate connector modes during init

When continuous splash is enabled, KMS populates the modes of
a connector during splash config. With TUI VM enabled, this path
will also be exercised by trusted vm for splash handoff, where for
a given display we try to use the same HW blocks configured by
the primary VM.

Since the trusted VM invokes the path under connection_mutex lock,
calling fill_modes will lead to a deadlock. So, move the connector
mode population during init for DSI displays, since the modes are
available for the connector during initialization.

Change-Id: I12f920f4af84b7bccc97a5f5edb5117ada49b960
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>