genericirq.tmpl: convert it to ReST

Brainless conversion of genericirq.tmpl book to ReST, via
	Documentation/sphinx/tmplcvt

Copyright information inserted manually.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>