powerpc/smp: Add check for kcalloc() failure in parse_thread_groups()

As kcalloc() may fail, check its return value to avoid a NULL pointer
dereference when passing it to of_property_read_u32_array().

Fixes: 790a166 ("powerpc/smp: Parse ibm,thread-groups with multiple properties")
Cc: stable@vger.kernel.org
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250923133235.1862108-1-lgs201920130244@gmail.com

Author: lgs2513

arch/powerpc/kernel/smp.c

@@ -822,6 +822,8 @@ static int parse_thread_groups(struct device_node *dn,
 
 	count = of_property_count_u32_elems(dn, "ibm,thread-groups");
 	thread_group_array = kcalloc(count, sizeof(u32), GFP_KERNEL);
+	if (!thread_group_array)
+		return -ENOMEM;
 	ret = of_property_read_u32_array(dn, "ibm,thread-groups",
 					 thread_group_array, count);
 	if (ret)