powerpc: iseries: Fix a bogus comment

A comment in lpevents.c refers to code that's actually in HvCallEvent.h.
The code in HvCallEvent.h is pretty obvious, so just remove the comment
altogether.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Stephen Rothwell <sfr@canb.auug.org.au>