Fix an unused variable warning.

Move the update of the loopfilter info to the same block where it
is used. GCC 4.5 is not able trace the initialization of the local
filter_info across the other calls between the two conditionals on
pbi->common and issues an uninitialized variable warning.

Change-Id: Ie4487b3714a096b3fb21608f6b0c74e745e3c6fc