irqflags-tracing.txt: standardize document format

Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx:

There isn't much to be done here: just mark the document
title as such and add a :Author:.

While here, use upper case at the beginning of a few paragraphs
that start with lower case.
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

Documentation/irqflags-tracing.txt

+=======================
 IRQ-flags state tracing
+=======================
 
-started by Ingo Molnar <mingo@redhat.com>
+:Author: started by Ingo Molnar <mingo@redhat.com>
 
-the "irq-flags tracing" feature "traces" hardirq and softirq state, in
+The "irq-flags tracing" feature "traces" hardirq and softirq state, in
 that it gives interested subsystems an opportunity to be notified of
 every hardirqs-off/hardirqs-on, softirqs-off/softirqs-on event that
 happens in the kernel.
@@ -14,7 +16,7 @@ CONFIG_PROVE_RWSEM_LOCKING will be offered on an architecture - these
 are locking APIs that are not used in IRQ context. (the one exception
 for rwsems is worked around)
 
-architecture support for this is certainly not in the "trivial"
+Architecture support for this is certainly not in the "trivial"
 category, because lots of lowlevel assembly code deal with irq-flags
 state changes. But an architecture can be irq-flags-tracing enabled in a
 rather straightforward and risk-free manner.
@@ -41,7 +43,7 @@ irq-flags-tracing support:
   excluded from the irq-tracing [and lock validation] mechanism via
   lockdep_off()/lockdep_on().
 
-in general there is no risk from having an incomplete irq-flags-tracing
+In general there is no risk from having an incomplete irq-flags-tracing
 implementation in an architecture: lockdep will detect that and will
 turn itself off. I.e. the lock validator will still be reliable. There
 should be no crashes due to irq-tracing bugs. (except if the assembly