riscv: add Sifive p550/p650 identification

Reviewed-by: Warner Losh <imp@FreeBSD.org>
Pull-Request: https://github.com/freebsd/freebsd-src/pull/1674

sys/riscv/include/cpu.h

@@ -80,6 +80,7 @@
 
 /* SiFive marchid values */
 #define	MARCHID_SIFIVE_U7	MARCHID_COMMERCIAL(7)
+#define	MARCHID_SIFIVE_P5	MARCHID_COMMERCIAL(8)
 
 /*
  * MMU virtual-addressing modes. Support for each level implies the previous,

sys/riscv/riscv/identcpu.c

@@ -126,6 +126,7 @@ static const struct marchid_entry global_marchids[] = {
 
 static const struct marchid_entry sifive_marchids[] = {
 	{ MARCHID_SIFIVE_U7,	"6/7/P200/X200-Series Processor" },
+	{ MARCHID_SIFIVE_P5,	"P550/P650 Processor" },
 	MARCHID_END
 };