The dump command for reading a region passes a requested read length
specified in words (4-byte units). The response overwrites the same field
with the actual number of bytes read.

The mailbox handler for DUMP which reads VPD data (region 23) is treating
the response field as if it were still a word_cnt, thus multiplying it by 4
to set the read's "length". Given the read value was calculated based on
the size of the read buffer, the longer response length runs off the end of
the buffer.

Fix by reworking the code to use the response field as a byte count.

Link: https://lore.kernel.org/r/20210421234511.102206-1-jsmart2021@gmail.comCo-developed-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: Justin Tee <justin.tee@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>