tools/intel_vbt_decode: Decode block 3 (Display Toggle Option)

Decode VBT block 3 (Display Toggle Option).

On ALM the block appears to contain some kind of actual toggle
list of child devices, on all more modern machines it just has
the feature bits.

Example output from ALM:
BDB block 3 (27 bytes, min 3 bytes) - Display toggle option block:
        0000: 03 1b 00 00 0c 00 08 00  01 00 09 00 02 00 00 00
        0010: 00 00 00 00 00 00 00 00  00 00 00 00 00 00

        Feature bits: 0x00
        Num entries: 12
        Toggle list #1: LFP1 (0x0008)
        Toggle list #2: CRT (0x0001)
        Toggle list #3: CRT,LFP1 (0x0009)
        Toggle list #4: TV (0x0002)
        Toggle list #5: none (0x0000)
        Toggle list #6: none (0x0000)
        Toggle list #7: none (0x0000)
        Toggle list #8: none (0x0000)
        Toggle list #9: none (0x0000)
        Toggle list #10: none (0x0000)
        Toggle list #11: none (0x0000)
        Toggle list #12: none (0x0000)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>