boot: driver chatter goes to the log; the console clears its margins

ACPI, DMI, SMP, xHCI, USB, I2C, NVMe, r8169 and ramdisk progress lines are
kinfo now: in dmesg and on a verbose boot, off the screen of a working
machine. Failures stay cprintf.

vt_repaint also paints the strip right of the last column and below the
last row, which kept the bottom of the X desktop after Ctrl+Alt+F-key.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4

kernel/drivers/gpu/vga/vga_fb.c

@@ -187,7 +187,7 @@ vga_disp_acquire(struct device *d, uint32 *stride_out)
     return 0;
   }
   memset(back, 0, back_bytes);
-  cprintf("display: %d KB back buffer, double buffered\n",
+  kinfo("display: %d KB back buffer, double buffered\n",
           (int)(back_bytes / 1024));
   return back;
 }