drm/amdgpu: Use flexible array member

Use flexible array member in ip discovery struct as recommended[1].

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#zero-length-and-one-element-arrays

v2: squash in struct_size fixes

Signed-off-by: Lijo Lazar <[e-mail]>
Reviewed-by: Christian König <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c

···
                                 }
                         }
 next_ip:
-			ip_offset += sizeof(*ip) + 4 * (ip->num_base_address - 1);
+			ip_offset += struct_size(ip, base_address, ip->num_base_address);
 		}
 	}
 }
···
 			res = kobject_add(&ip_hw_instance->kobj, NULL,
 					  "%d", ip_hw_instance->num_instance);
 next_ip:
-			ip_offset += sizeof(*ip) + 4 * (ip->num_base_address - 1);
+			ip_offset += struct_size(ip, base_address, ip->num_base_address);
 		}
 	}
 
···
 			}
 
 next_ip:
-			ip_offset += sizeof(*ip) + 4 * (ip->num_base_address - 1);
+			ip_offset += struct_size(ip, base_address, ip->num_base_address);
 		}
 	}
 
···
 					*revision = ip->revision;
 				return 0;
 			}
-			ip_offset += sizeof(*ip) + 4 * (ip->num_base_address - 1);
+			ip_offset += struct_size(ip, base_address, ip->num_base_address);
 		}
 	}
 

drivers/gpu/drm/amd/include/discovery.h

···
 	uint8_t harvest : 4;      /* Harvest */
 	uint8_t reserved : 4;     /* Placeholder field */
 #endif
-	uint32_t base_address[1]; /* variable number of Addresses */
+	uint32_t base_address[]; /* variable number of Addresses */
 } ip;
 
 typedef struct die_header