x86/HPET: reduce hpet_next_event() call sites

I'm surprised gcc doesn't manage to do that: At least in debug builds two
call sites exist, just like source code has it. That's not necessary
though - by using do/while we can reduce this to a single call site. Then
the function will be inlined.

While improving code gen, also switch the function's 2nd parameter to
unsigned.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Roger Pau Monné <roger.pau@citrix.com>

xen/arch/x86/hpet.c

@@ -124,7 +124,7 @@ static inline unsigned long ns2ticks(unsigned long nsec, int shift,
     return (unsigned long) tmp;
 }
 
-static int hpet_next_event(unsigned long delta, int timer)
+static int hpet_next_event(unsigned long delta, unsigned int timer)
 {
     uint32_t cnt, cmp;
     unsigned long flags;
@@ -173,12 +173,10 @@ static int reprogram_hpet_evt_channel(
     delta = max_t(int64_t, delta, MIN_DELTA_NS);
     delta = ns2ticks(delta, ch->shift, ch->mult);
 
-    ret = hpet_next_event(delta, ch->idx);
-    while ( ret && force )
-    {
-        delta += delta;
+    do {
         ret = hpet_next_event(delta, ch->idx);
-    }
+        delta += delta;
+    } while ( ret && force );
 
     return ret;
 }