powerpc: Fix P10 PVR revision in /proc/cpuinfo for SMT4 cores

On POWER10 bit 12 in the PVR indicates if the core is SMT4 or SMT8.
Bit 12 is set for SMT4.

Without this patch, /proc/cpuinfo on a SMT4 DD1 POWER10 looks like
this:
  cpu             : POWER10, altivec supported
  revision        : 17.0 (pvr 0080 1100)

Fixes: a3ea40d ("powerpc: Add POWER10 architected mode")
Cc: [email protected] # v5.8
Signed-off-by: Michael Neuling <[email protected]>
Reviewed-by: Vaidyanathan Srinivasan <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: mikey

arch/powerpc/kernel/setup-common.c

@@ -311,6 +311,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 				min = pvr & 0xFF;
 				break;
 			case 0x004e: /* POWER9 bits 12-15 give chip type */
+			case 0x0080: /* POWER10 bit 12 gives SMT8/4 */
 				maj = (pvr >> 8) & 0x0F;
 				min = pvr & 0xFF;
 				break;