[system][hid] add input descriptor parsing

.. to the hid app which grows a "parse <device> option
example from QEMU:

$ hid parse /dev/class/input/001
hid: report descriptor len=50
hid: report descriptor:
Item(Global, UsagePage): 0x1
Item(Local, Usage): 0x2
Item(Main, Collection): 0x1
Item(Local, Usage): 0x1
Item(Main, Collection): 0
Item(Global, UsagePage): 0x9
Item(Local, UsageMinimum): 0x1
Item(Local, UsageMaximum): 0x3
Item(Global, LogicalMinimum): 0
Item(Global, LogicalMaximum): 0x1
Item(Global, ReportCount): 0x3
Item(Global, ReportSize): 0x1
Item(Main, Input): 0x2
Item(Global, ReportCount): 0x1
Item(Global, ReportSize): 0x5
Item(Main, Input): 0x1
Item(Global, UsagePage): 0x1
Item(Local, Usage): 0x30
Item(Local, Usage): 0x31
Item(Global, LogicalMinimum): 0x81
Item(Global, LogicalMaximum): 0x7f
Item(Global, ReportSize): 0x8
Item(Global, ReportCount): 0x2
Item(Main, Input): 0x6
Item(Main, EndCollection): 0
Item(Main, EndCollection): 0

Change-Id: I1332fa1752a15906802b21c0e7b7929102cf9434