[BUG] drivers/tty/hvc: a possible sleep-in-atomic bug in xen_pv_console_init

According to drivers/tty/hvc/hvc_xen.c, the kernel module may sleep 
under a spinlock.
The function call path is:
xen_pv_console_init (acquire the spinlock)
   xencons_info_pv_init
     gfn_to_virt (gfn_to_pfn) --> may sleep

I do not find a good way to fix it, so I only report.
This possible bug is found by my static analysis tool (DSAC) and my code 
review.


Thanks,
Jia-Ju Bai