hwmon: (powerpc/powernv) hwmon driver for power, fan rpm, voltage and temperature

hwmon: (powerpc/powernv) hwmon driver for power, fan rpm, voltage and temperature

This patch adds basic kernel support for reading power values, fan
speed rpm, voltage and temperature data on powernv platforms which
will be exported to user space through sysfs interface.

Test results:
-------------
[root@tul163p1 ~]# sensors
ibmpowernv-isa-0000
Adapter: ISA adapter
fan1:        5465 RPM  (min =    0 RPM)
fan2:        5152 RPM  (min =    0 RPM)
fan3:        5521 RPM  (min =    0 RPM)
fan4:        4891 RPM  (min =    0 RPM)
fan5:           0 RPM  (min =    0 RPM)
fan6:           0 RPM  (min =    0 RPM)
fan7:        7480 RPM  (min =    0 RPM)
fan8:        7944 RPM  (min =    0 RPM)
temp1:        +39.0°C  (high =  +0.0°C)
power1:      190.00 W

[root@tul163p1 ~]# ls /sys/devices/platform/
alarmtimer  ibmpowernv.0  power  rtc-generic  serial8250  uevent
[root@tul163p1 ~]# ls /sys/devices/platform/ibmpowernv.0/hwmon/hwmon0/
device	    fan2_min	fan4_min    fan6_min	fan8_min   power
fan1_fault  fan3_fault	fan5_fault  fan7_fault	in1_fault  power1_input
fan1_input  fan3_input	fan5_input  fan7_input	in2_fault  subsystem
fan1_min    fan3_min	fan5_min    fan7_min	in3_fault  temp1_input
fan2_fault  fan4_fault	fan6_fault  fan8_fault	in4_fault  temp1_max
fan2_input  fan4_input	fan6_input  fan8_input	name	   uevent
[root@tul163p1 ~]# ls /sys/class/hwmon/hwmon0/
device	    fan2_min	fan4_min    fan6_min	fan8_min   power
fan1_fault  fan3_fault	fan5_fault  fan7_fault	in1_fault  power1_input
fan1_input  fan3_input	fan5_input  fan7_input	in2_fault  subsystem
fan1_min    fan3_min	fan5_min    fan7_min	in3_fault  temp1_input
fan2_fault  fan4_fault	fan6_fault  fan8_fault	in4_fault  temp1_max
fan2_input  fan4_input	fan6_input  fan8_input	name	   uevent
[root@tul163p1 ~]#

Signed-off-by: Neelesh Gupta <neelegup@linux.vnet.ibm.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>