gpu: host1x: Improve debug disassembly formatting

The host1x driver prints out "disassembly" dumps of the command FIFO
and gather contents on submission timeouts. However, the output has
been quite difficult to read with unnecessary newlines and occasional
missing parentheses.

Fix these problems by using pr_cont to remove unnecessary newlines
and by fixing other small issues.

Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
Reviewed-by: Dmitry Osipenko <digetx@gmail.com>
Tested-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>