GKI: drm: samsung: consume MIPI_DSI_MSG_LASTCOMMAND flag

GKI support for MIPI_DSI_MSG_LASTCOMMAND flag was reverted on commit
bf72df2331343 ("Revert "ANDROID: drivers: gpu: drm: add support to batch
commands")". This patch restores such flag definition internally as a
temporary solution.

Bug: 201090883
Signed-off-by: Carlos Llamas <cmllamas@google.com>
Change-Id: I3b97bd561a0fdb3e633cca8c2df5c701b2948503