avcodec/jpeglsdec: Check run value more completely in ls_decode_line()

previously it could have been by 1 too large
Fixes out of array access
Fixes: asan_heap-oob_12240f5_1_asan_heap-oob_12240f5_448_t8c1e3.jls
Fixes: asan_heap-oob_12240f5_1_asan_heap-oob_12240f5_448_t8nde0.jls
Fixes: asan_heap-oob_12240fa_1_asan_heap-oob_12240fa_448_t16e3.jls

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
