I was looking at this myself last night
If you try lspci -v you get a bit more info.
The signal processor is using the 'pciPTI' kernel driver and when I googled it I found this: (https://lkml.org/lkml/2011/2/8/296)
00:12.0 Signal processing controller: Intel Corporation Device 119f (rev 01)
Flags: fast devsel, IRQ 46
Memory at f9009000 (32-bit, non-prefetchable) [size=4K]
Memory at f90a0000 (32-bit, non-prefetchable) [size=64K]
Memory at fa000000 (32-bit, non-prefetchable) [size=16M]
Capabilities: [b0] Power Management version 3
Capabilities: [b8] Vendor Specific Information: Len=08 <?>
Capabilities: [c0] PCI-X non-bridge device
Capabilities: [100] Vendor Specific Information: ID=0000 Rev=0 Len=024 <?>
Kernel driver in use: pciPTI
Considering the size of the memory regions of the first display controller I'd guess that's the disabled (PowerVR?) GPU. This one would be sweet if we could use, not for graphics(I don't think graphics interfaces are exposed on the 70 pin connector) but for computing since from what I read It's OpenCL capable (I could be totally wrong about this but on wikipedia it says edison uses Z34XX, and this document says http://download.intel.com/newsroom/kits/atom/comms/pdfs/Intel_Atom_Z34XX_ProductBrief.pdf it's capable of OpenCL)
00:02.0 Display controller: Intel Corporation Device 1182 (rev 01)
Flags: bus master, fast devsel, latency 0
Memory at c0000000 (32-bit, non-prefetchable) [size=32M]
Memory at 80000000 (32-bit, non-prefetchable) [size=256M]
I/O ports at 7ff8 [size=8]
Capabilities: [d0] Power Management version 2
Capabilities: [b0] Vendor Specific Information: Len=07 <?>
Capabilities: [90] MSI: Enable- Count=1/1 Maskable- 64bit-