The missing new line is likely related to undefined device name in the driver. An old viadrm driver was taking it from drm pciids. However, this information would be just a duplicate to the vga driver itself which prints device information, thus just adding a new line seems to be relevant fix. This patch works for me:
diff --git a/sys/external/bsd/drm2/via/via_pci.c b/sys/external/bsd/drm2/via/via_pci.c
--- a/sys/external/bsd/drm2/via/via_pci.c
+++ b/sys/external/bsd/drm2/via/via_pci.c
@@ -116,6 +116,9 @@ viadrm_attach(device_t parent, device_t self, void *aux)
KASSERT(cookiep != NULL);
+ aprint_naive("\n");
+ aprint_normal("\n");
+
if (!pmf_device_register(self, NULL, NULL))
aprint_error_dev(self, "couldn't establish power handler\n");
relevant dmesg part after the patch:
...
pci1 at ppb0 bus 1
pci1: i/o space, memory space enabled
vga0 at pci1 dev 0 function 0: VIA Technologies product 3118 (rev. 0x02)
wsdisplay0 at vga0 kbdmux 1: console (80x25, vt100 emulation)
wsmux1: connecting to wsdisplay0
viadrmums0 at vga0
kern info: [drm] Supports vblank timestamp caching Rev 2 (21.10.2013).
kern info: [drm] No driver support for vblank timestamp query.
...