x86: Fix typo s/ECLR/ELCR/ for the PIC register

The proper spelling for the acronym referring to the Edge/Level Control 
Register is ELCR rather than ECLR.  Adjust references accordingly.  No 
functional change.

Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2107200251080.9461@angie.orcam.me.uk