Display CPU model in dmesg on mips targets

Also, save the CPU model for atheros ar531x boards.

Submitted by: Hiroki Mori
Differential Revision: https://reviews.freebsd.org/D20371

sys/mips/atheros/ar531x/ar5315_machdep.c

@@ -146,6 +146,8 @@ SYSCTL_STRING(_hw_device, OID_AUTO, revision, CTLFLAG_RD, hw_device_revision, 0,
 	   "Board revision");
 #endif
 
+extern char cpu_model[];
+
 void
 platform_start(__register_t a0 __unused, __register_t a1 __unused, 
     __register_t a2 __unused, __register_t a3 __unused)
@@ -260,6 +262,8 @@ platform_start(__register_t a0 __unused, __register_t a1 __unused,
 	printf("  a2 = %08x\n", a2);
 	printf("  a3 = %08x\n", a3);
 
+	strcpy(cpu_model, ar5315_get_system_type());
+
 	/*
 	 * XXX this code is very redboot specific.
 	 */

sys/mips/mips/machdep.c

@@ -186,6 +186,8 @@ cpu_startup(void *dummy)
 	if (boothowto & RB_VERBOSE)
 		bootverbose++;
 
+	printf("CPU model: %s\n", cpu_model);
+
 	printf("real memory  = %ju (%juK bytes)\n", ptoa((uintmax_t)realmem),
 	    ptoa((uintmax_t)realmem) / 1024);