msm: mdss: fix solid fill programming on pipe

Format on pipe is changed to solid fill when it is
un-staged from mixer and put in cleanup list. This is
not required because HW is not going to pick up this pipe
when it is not present on any stage. This change removes
the unnecessary programming during cleanup and updates the
sw pixel extension configuration for solid fill pipe.

Change-Id: Idabd264dc9a3e93ef94e347e7f48fd6f88bd987b
Signed-off-by: Dhaval Patel <pdhaval@codeaurora.org>