x86, hwmon: Package Level Thermal/Power: pkgtemp hwmon driver

This patch adds a hwmon driver for package level thermal control. The driver
dumps package level thermal information through sysfs interface so that upper
level application (e.g. lm_sensor) can retrive the information.

Instead of having the package level hwmon code in coretemp, I write a seperate
driver pkgtemp because:

First, package level thermal sensors include not only sensors for each core,
but also sensors for uncore, memory controller or other components in the
package. Logically it will be clear to have a seperate hwmon driver for package
level hwmon to monitor wider range of sensors in a package. Merging package
thermal driver into core thermal driver doesn't make sense and may mislead.

Secondly, merging the two drivers together may cause coding mess. It's easier
to include various package level sensors info if more sensor information is
implemented. Coretemp code needs to consider a lot of legacy machine cases.
Pkgtemp code only considers platform starting from Sandy Bridge.

On a 1Sx4Cx2T Sandy Bridge platform, lm-sensors dumps the pkgtemp and coretemp:

pkgtemp-isa-0000
Adapter: ISA adapter
physical id 0: +33.0°C  (high = +79.0°C, crit = +99.0°C)

coretemp-isa-0000
Adapter: ISA adapter
Core 0:      +32.0°C  (high = +79.0°C, crit = +99.0°C)

coretemp-isa-0001
Adapter: ISA adapter
Core 1:      +32.0°C  (high = +79.0°C, crit = +99.0°C)

coretemp-isa-0002
Adapter: ISA adapter
Core 2:      +32.0°C  (high = +79.0°C, crit = +99.0°C)

coretemp-isa-0003
Adapter: ISA adapter
Core 3:      +32.0°C  (high = +79.0°C, crit = +99.0°C)

[ hpa: folded v3 patch removing improper global variable "SHOW" ]

Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
LKML-Reference: <1280448826-12004-3-git-send-email-fenghua.yu@intel.com>
Reviewed-by: Len Brown <len.brown@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>