lguest files should explicitly include asm/paravirt.h

Files using bits from paravirt.h should explicitly include it rather than
relying on it being pulled in by something else.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>