by replacing it with a multiplication. Said multiplication can't
overflow an int32_t because lpc_coefs is limited to 16 bit precision.

Fixes the FACE-test acodec-ra144 as well as part of #8217.
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>