sbc: Fix for SBC encoding with block sizes other than 16
sbc: Fix for SBC encoding with block sizes other than 16

Thanks to Christian Hoene for finding and reporting the
problem. This regression was intruduced in commit
19af3c49e61aa046375497108e05a3a0605da158

pstglia/external-bluetooth-sbc,pstglia/external-bluetooth-sbc