Fix cmdline setup in fatvbr

boot/fatvbr.asm

@@ -273,9 +273,18 @@ parse_cmdline:
 .args_start:
   mov di, (psp + 0x81)
 .args_loop:
-  call .read
+  lodsb
+  test al, al
+  jz .args_end
   stosb
   jmp .args_loop
+.args_end:
+  mov ax, di
+  sub ax, (psp + 0x81)
+  mov [psp+0x80], al
+  mov al, 0x0D
+  stosb
+  ret
 .read:
   lodsb
   test al, al
@@ -285,7 +294,7 @@ parse_cmdline:
   ret
 
 cmdline:
-  db "KERNEL.COM /?", 0
+  db CMDLINE, 0
 
 times (0x1FE - ($-$$)) db 0