linux/irq.h uses EINVAL but does not #include linux/errno.h.  This results in
the compiler spitting out errors on some files.
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>