habanalabs: fix memory leak with CBs with unaligned size

This patch fix a bug when a command buffer with unaligned size (with
regard to PAGE_SIZE) was used. The accounting for the unmap operation
wasn't done correctly and could result in a memory leak.

Signed-off-by: Oded Gabbay <oded.gabbay@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>