lima: remove partial clear support from pipe->clear()

pipe->clear() is not called for partial clears, which mesa emulates by
drawing a quad.
Furthermore, drivers should not use rasterizer state information for
scissor information (which was being used to handle the partial clears).
So, remove the partial clear support since it was not supposed to be
handled by pipe->clear() anyway.
This fixes issues with clearing after switching to different sized
framebuffers.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Reviewed-by: Vasily Khoruzhick <anarsoul@gmail.com>
Reviewed-by: Qiang Yu <yuq825@gmail.com>
40 jobs for !2055 with lima-scissors-clear in 18 minutes and 53 seconds (queued for 3 seconds)
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