x86, hpet: Simplify the HPET code

On 64-bits, using unsigned long when unsigned int suffices
needlessly creates larger code (due to the need for REX
prefixes), and most of the logic in hpet.c really doesn't need
64-bit operations.

At once this avoids the need for a couple of type casts.

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Shaohua Li <shaohua.li@intel.com>
Cc: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
LKML-Reference: <4A8BC9780200007800010832@vpn.id2.novell.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>