[MIPS] modify the MIPS CPU classfication

#define PRID_IMP_RM7000		0x2700

#define PRID_IMP_NEVADA		0x2800		/* RM5260 ??? */

#define PRID_IMP_RM9000		0x3400

#define PRID_IMP_LOONGSON1	0x4200

#define PRID_IMP_R5432		0x5400

#define PRID_IMP_R5500		0x5500

#define PRID_IMP_LOONGSON2	0x6300

#define PRID_IMP_UNKNOWN	0xff00

#define PRID_IMP_24KE		0x9600

#define PRID_IMP_74K		0x9700

#define PRID_IMP_1004K		0x9900

#define PRID_IMP_LOONGSON1      0x4200

#define PRID_IMP_LOONGSON2      0x6300

/*

 * These are the PRID's for when 23:16 == PRID_COMP_SIBYTE