Resolve QAT issues with incompressible data

Resolve QAT issues with incompressible data

Currently, when ZFS wants to accelerate compression with QAT, it
passes a destination buffer of the same size as the source buffer.
Unfortunately, if the data is incompressible, QAT can actually
"compress" the data to be larger than the source buffer. When this
happens, the QAT driver will return a FAILED error code and print
warnings to dmesg. This patch fixes these issues by providing the
QAT driver with an additional buffer to work with so that even
completely incompressible source data will not cause an overflow.

This patch also resolves an error handling issue where
incompressible data attempts compression twice: once by QAT and
once in software. To fix this issue, a new (and fake) error code
CPA_STATUS_INOMPRESSIBLE has been added so that the calling code
can correctly account for the difference between a hardware
failure and data that simply cannot be compressed.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Weigang Li <weigang.li@intel.com>
Signed-off-by: Tom Caputi <tcaputi@datto.com>
Closes #7338