[PATCH] uml: replace printk with "stack-friendly" printf - to report console failure

User get *a lot* confused when consoles don't work but we don't report
anything.  And, as reported in the comment, using printk to report "your
console doesn't work" isn't likely to go that far.

Fix the problem on the base of this: stack consumption by host printf().  Use
kernel sprintf() and os_write_file, using a wild guess that one page will be
enough for the message, to preallocate the buffer with kmalloc().

Signed-off-by: Paolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Jeff Dike <jdike@addtoit.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>