x86/APIC: reduce rounding errors in calculations

x86/APIC: reduce rounding errors in calculations

Dividing by HZ/10 just to subsequently multiply by HZ again in all uses
of the respective variable is pretty pointlessly introducing rounding
(really: truncation) errors. While transforming the respective
expressions it became apparent that "result" would be left unused except
for its use as function return value. As the sole caller of the function
doesn't look at the returned value, simply convert the function to have
"void" return type.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>