AFAIK IRQ number 0 is a perfectly valid IRQ number.  But it seems there are
numerous places where it's considered to be invalid or "no irq" value.  Since
that value is problematic, the IRQ mapping is changed to not use it.
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>