misc: pvpanic: move bit definition to uapi header file

Some processes outside of the kernel(Ex, QEMU) should know what the
value really is for, so move the bit definition to a uapi file.

Suggested-by: Greg KH <gregkh@linuxfoundation.org>
Signed-off-by: zhenwei pi <pizhenwei@bytedance.com>
Link: https://lore.kernel.org/r/20200102023513.318836-2-pizhenwei@bytedance.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>