Documentation: irq/concepts: Add commas and reflow

For easier reading, it is always desired to add commas at some places in
text. Like before adverbs or after fronted sentences.

[ tglx: Fix up subject prefix ]

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250319092951.37667-54-jirislaby@kernel.org