x86: HPET_MSI Basic HPET_MSI setup code

Basic HPET MSI setup code. Routines to perform basic MSI read write
in HPET memory map and setting up irq_chip for HPET MSI.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>