target/mips: Add CP0 BadInstrX register

target/mips: Add CP0 BadInstrX register

Add CP0 BadInstrX register. This register will be used in nanoMIPS.

Reviewed-by: Aleksandar Markovic <amarkovic@wavecomp.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Stefan Markovic <smarkovic@wavecomp.com>
Signed-off-by: Yongbok Kim <yongbok.kim@mips.com>
Signed-off-by: Aleksandar Markovic <amarkovic@wavecomp.com>