powerpc/powernv: Return for invalid IMC domain

Currently init_imc_pmu() can fail either because we try to register an
IMC unit with an invalid domain (i.e an IMC node not supported by the
kernel) or something went wrong while registering a valid IMC unit. In
both the cases kernel provides a 'Register failed' error message.

For example when trace-imc node is not supported by the kernel, but
skiboot advertises a trace-imc node we print:

  IMC Unknown Device type
  IMC PMU (null) Register failed

To avoid confusion just print the unknown device type message, before
attempting PMU registration, so the second message isn't printed.

Fixes: 8f95faaac5 ("powerpc/powernv: Detect and create IMC device")
Reported-by: Pavaman Subramaniyam <pavsubra@in.ibm.com>
Signed-off-by: Anju T Sudhakar <anju@linux.vnet.ibm.com>
Reviewed-by: Madhavan Srinivasan <maddy@linux.vnet.ibm.com>
[mpe: Reword change log a bit]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/platforms/powernv/opal-imc.c

@@ -161,6 +161,10 @@ static int imc_pmu_create(struct device_node *parent, int pmu_index, int domain)
 	struct imc_pmu *pmu_ptr;
 	u32 offset;
 
+	/* Return for unknown domain */
+	if (domain < 0)
+		return -EINVAL;
+
 	/* memory for pmu */
 	pmu_ptr = kzalloc(sizeof(*pmu_ptr), GFP_KERNEL);
 	if (!pmu_ptr)