Improve readability of USBHID related descriptors

[Ingramz]

Description

While debugging for another issue, I made some formatting changes to existing code to better understand it myself.

• Changed generic USBHID report descriptor to use predefined macros for descriptor field types/sizes which are already used in USBMouse and USBKeyboard. Compiled result is identical to previous code.
• Tweaked configuration descriptor formatting so they can be more easily diffed
  • Defined the remaining HID sublasses and protocols to provide give context to magic values
  • Aligned comments
  • Cleaned up redundancies in comments

Status

READY

Migrations

If this PR changes any APIs or behaviors, give a short description of what API users should do when this PR is merged.

NO

CLA has been signed https://developer.mbed.org/users/ingram/

[0xc0170]

How was this tested?

[0xc0170]

/morph test

[Ingramz]

I ran the USBHID example on LPC1768 and read the report descriptors using software called USBlyzer.

[bridadan]

/morph test

[mbed-bot]

Result: SUCCESS

Your command has finished executing! Here's what you wrote!

/morph test

Output

mbed Build Number: 1599

All builds and test passed!