unix: add HIDRAW ioctls

This change adds (most) of the ioctl API for the Linux HIDRAW interface.
Reading and writing non-numbered HID reports is done using the read and
write system calls respectively.

Some of the HIDIOC* request numbers are exported directly while others
are kept unexported. This is because some of the #defines require a len
attribute that doesn't have a specific well defined value.

Wrapper types are added for most of the request numbers as is standard.
No wrapper is added for HIDIOCGRDESCSIZE as it would just be
IoctlGetUint32.

The HIDIOC[GS]FEATURE, HIDIOC[GS]INPUT and HIDIOC[GS]OUTPUT request
numbers, which are required for numbered HID reports, are entirely
ommitted as the len attribute has to be a runtime variable. These could
be added later by doing something like
 `HIDIOCGFEATURE(0) | (len << _IOC_SIZESHIFT)`,
with care taken that len doesn't overflow _IOC_XSIZEMASK.

Outdated documentation for the HIDRAW interface is available at:
https://www.kernel.org/doc/Documentation/hid/hidraw.txt.

Change-Id: I2ae5060f0f46150f6fb52959c2e55f50927c1f69
Reviewed-on: https://go-review.googlesource.com/c/sys/+/289169
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>

unix/zerrors_linux_arm.go

@@ -93,6 +93,9 @@ const (
 	F_SETOWN                         = 0x8
 	F_UNLCK                          = 0x2
 	F_WRLCK                          = 0x1
+	HIDIOCGRAWINFO                   = 0x80084803
+	HIDIOCGRDESC                     = 0x90044802
+	HIDIOCGRDESCSIZE                 = 0x80044801
 	HUPCL                            = 0x400
 	ICANON                           = 0x2
 	IEXTEN                           = 0x8000
@@ -492,6 +495,9 @@ const (
 	WORDSIZE                         = 0x20
 	XCASE                            = 0x4
 	XTABS                            = 0x1800
+	_HIDIOCGRAWNAME                  = 0x80804804
+	_HIDIOCGRAWPHYS                  = 0x80404805
+	_HIDIOCGRAWUNIQ                  = 0x80404808
 )
 
 // Errors