xtensa: fix address check in dma_free_coherent

Virtual address is translated to the XCHAL_KSEG_CACHED region in the
dma_free_coherent, but is checked to be in the 0...XCHAL_KSEG_SIZE
range.

Cc: stable@vger.kernel.org
Signed-off-by: Alan Douglas <adouglas@cadence.com>
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>