drm/i915/hwmon: expose package temperature

Add hwmon support for temp1_input attribute, which will expose package
temperature in millidegree Celsius. With this in place we can monitor
package temperature using lm-sensors tool.

$ sensors
i915-pci-0300
Adapter: PCI adapter
in0:         990.00 mV
fan1:        1260 RPM
temp1:        +45.0°C
power1:           N/A  (max =  35.00 W)
energy1:      12.62 kJ

v2: Use switch case (Anshuman)
v3: Comment adjustment (Riana)

Closes: #11276


Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Reviewed-by: Riana Tauro <riana.tauro@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240910105242.3357276-1-raag.jadav@intel.com