qemu_log_mask() and error_report() are preferred over fprintf() for
logging errors.  Also remove square brackets [] and additional new line
characters in printed messages.

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20170313184750.429-2-krzk@kernel.org
[PMM: wrapped long line]
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>