The MV decoding changes in c5fb0eb8 introduced a bug where the
macroblock clamping state was reset for each partition, so if an
earlier partition needed clamping but a subsequent one didn't,
the MB wouldn't receive clamping. Instead, the state is only
set during splitmv decoding, never cleared.

Change-Id: I224fe258493405ee0f6a04596acdb622c475e845