filter_mb_mbaff_edgev() and filter_mb_mbaff_edgecv()
have a function parameter whose expected size depends upon
another parameter: It is 2 * bsi + 1 (with bsi always being 1 or 2).
This array is declared as const int16_t[7], yet some of the callers
with bsi == 1 call it with only an const int16_t[4] available.
This leads to -Wstringop-overread warnings from GCC 12.1.

This commit fixes these by replacing [7] with [/* 2 * bsi + 1 */],
so that the expected range and its dependence on bsi is immediately
visible.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>