irqtop: add total and delta as own columns

irqtop: add total and delta as own columns

This commit add total and delta as separate columns rather than a toggle,
making output generally more informative.  When using command I found that
sort order key bindings should match with first letter of column headers so
that they are as easy as possible to remember, and therefore enhancing user
experience.

Requested-by: Karel Zak <kzak@redhat.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>