ia64: replace comments with C99 initializers

This replaces comments with C99's designated initializers because the
kernel supports them now.

Link: https://lkml.kernel.org/r/20220326165909.506926-3-benni@stuerz.xyz


Signed-off-by: Benjamin Stürz <benni@stuerz.xyz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>