[9fans] AMD cpu detection

[forsyth@caldo.demon.co.uk forsyth@caldo.demon.co.uk]

for a 233MHz AMD/K6, on a Micronics AT-03 Twister m/board, i now use:
	{ 5,	6,	11,	"AMD-K6", },	/* determined by trial and error */
which might imply this improved approximation for the other plain K6 entry:
	{ 5,	7,	11,	"AMD-K6", },	/* guesswork */
(but i haven't got that model here).  i'll try it on a 200MHz K6 when i get to
the office.

on boot, i get
	cpu0: 234MHz AuthenticAMD AMD-K6 (cpuid: AX 0x0562 DX: 0x8001BF)
reducing 11 to 10 aalcycles gave 214MHz, so i use 11.

further retrofitting changes required to get that far:

	void
	printcpufreq(void)
	{
		int i;
		char buf[128];

		i = sprint(buf, "cpu%d: %dMHz ", m->machno, cpumhz);
		if(cpuidid[0])
			i += sprint(buf+i, "%s ", cpuidid);
		sprint(buf+i, "%s (cpuid: AX 0x%4.4luX DX 0x%4.4luX)\n",
			cputype->name, cpuidax, cpuiddx);
		print(buf);
	}

ie: delete m-> from several names to refer to the newly added static variables.

add

	#define X86STEPPING(x)	((x) & 0x0F)
	#define X86MODEL(x)	(((x)>>4) & 0x0F)
	#define X86FAMILY(x)	(((x)>>8) & 0x0F)

to the top of io.h

and put

	#define CPUID		BYTE $0x0F; BYTE $0xA2	/* CPUID, argument in AX */

after
	#define NOP	XCHGL	AX,AX

in l.s

i think that's all i did to get it to work.