riscv: mm: don't advertise 1 num_asid for 0 asid bits

Even if mmu doesn't support ASID, current code calculates @num_asids=1
which is misleading, so avoid setting any asid related variables in such
case.

Also while here, print the number of asid bits discovered even for the
disabled case.

Verified this on Hifive Unmatched.
Reviewed-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Vineet Gupta <vgupta@kernel.org>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

arch/riscv/mm/context.c

@@ -233,8 +233,10 @@ static int __init asids_init(void)
 	local_flush_tlb_all();
 
 	/* Pre-compute ASID details */
-	num_asids = 1 << asid_bits;
-	asid_mask = num_asids - 1;
+	if (asid_bits) {
+		num_asids = 1 << asid_bits;
+		asid_mask = num_asids - 1;
+	}
 
 	/*
 	 * Use ASID allocator only if number of HW ASIDs are
@@ -255,7 +257,7 @@ static int __init asids_init(void)
 		pr_info("ASID allocator using %lu bits (%lu entries)\n",
 			asid_bits, num_asids);
 	} else {
-		pr_info("ASID allocator disabled\n");
+		pr_info("ASID allocator disabled (%lu bits)\n", asid_bits);
 	}
 
 	return 0;