MIPS: Add define for Config.VI (virtual icache) bit

The Config.VI bit specifies that the instruction cache is virtually
tagged, which is checked in c-r4k.c's probe_pcache(). Add a proper
definition for it in mipsregs.h and make use of it.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/mips/include/asm/mipsregs.h

@@ -533,6 +533,7 @@
 #define TX49_CONF_CWFON		(_ULCAST_(1) << 27)
 
 /* Bits specific to the MIPS32/64 PRA.	*/
+#define MIPS_CONF_VI		(_ULCAST_(1) <<  3)
 #define MIPS_CONF_MT		(_ULCAST_(7) <<	 7)
 #define MIPS_CONF_MT_TLB	(_ULCAST_(1) <<  7)
 #define MIPS_CONF_MT_FTLB	(_ULCAST_(4) <<  7)

arch/mips/mm/c-r4k.c

@@ -1206,7 +1206,7 @@ static void probe_pcache(void)
 			      c->icache.linesz;
 		c->icache.waybit = __ffs(icache_size/c->icache.ways);
 
-		if (config & 0x8)		/* VI bit */
+		if (config & MIPS_CONF_VI)
 			c->icache.flags |= MIPS_CACHE_VTAG;
 
 		/*