ms_adpcm: Fix and extend size checks
ms_adpcm: Fix and extend size checks

'blockalign' is the size of a block, and each block contains 7 samples
per channel as part of the preamble, so check against 'samplesperblock'
rather than 'blockalign'. Also add an additional check that the block
is big enough to hold the samples it claims to hold.

https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=26803

erikd/libsndfile,libsndfile/libsndfile,libsndfile/libsndfile,libsndfile/libsndfile,libsndfile/libsndfile,erikd/libsndfile,evpobr/libsndfile,evpobr/libsndfile,erikd/libsndfile,evpobr/libsndfile,erikd/libsndfile,erikd/libsndfile,libsndfile/libsndfile,evpobr/libsndfile,evpobr/libsndfile