ACPI: DPTF: Add new PCH FIVR methods

ACPI: DPTF: Add new PCH FIVR methods

Some additional information is required for updating PCH FIVR values
upon WiFi channel changes.

New attributes added to the existing sysfs:

fivr_switching_freq_mhz	: Get the FIVR switching control frequency
			  using ACPI method GFCS. Refer to the
			  documentation for the equation.

fivr_switching_fault_status: Read the FIVR switching frequency control
			fault status. Uses ACPI method GFFS

ssc_clock_info : Presents SSC (spread spectrum clock) information for EMI
		(Electro magnetic interference) control. Use ACPI method
		GEMI. Refer to the description of GEMI method below.

GFCS
This ACPI method is used to read the FIVR switching control
frequency.
Bits	Description
[11:0]	Actual Frequency = value * XTAL_FREQ / 128
[31:12]	Reserved

GFFS
This ACPI method is used to read the FIVR switching frequency control
fault status.
Bits	Description
[0:0]	Fault status when set to 1
[31:1]	Reserved

GEMI
This ACPI method is used to read the programmed register value for EMI
(Electro magnetic interference) control.

Bits	Description
[7:0]	Sets clock spectrum spread percentage:
	0x00=0.2% , 0x3F=10%
	1 LSB = 0.1% increase in spread (for
	settings 0x01 thru 0x1C)
	1 LSB = 0.2% increase in spread (for
	settings 0x1E thru 0x3F)
[8]	When set to 1, enables spread
	spectrum clock
[9]	0: Triangle mode. FFC frequency
	walks around the Fcenter in a linear
	fashion
	1: Random walk mode. FFC frequency
	changes randomly within the SSC
	(Spread spectrum clock) range
[10]	0: No white noise. 1: Add white noise
	to spread waveform
[11]	When 1, future writes are ignored.

Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Changelog and pch_fivr_switch_frequency documentation edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>