ENGR00233780 ASRC: limit output buffer size to avoid kernel dump

ENGR00233780 ASRC: limit output buffer size to avoid kernel dump

For ASRC memory to memory transfer, user would send driver input buffer
and driver would copy converted output buffer into user's buffer.
However, ASRC can't promise the ratio of output buffer size/input buffer
size being equal to output sample rate/input sample rate.e.g, for
convert from 8k to 48k and 1000 bytes input buffer size, ASRC may pop
out 5999 bytes or 6001 bytes. If driver copy all 6001 bytes into user's
buffer, kernel dump may happens cause of accessing unexisted buffer.

In this patch, if ASRC output buffer size is larger than user's buffer
size, discard exact part.

Signed-off-by: Chen Liangjun <b36089@freescale.com>