In /usr/local/share/urjtag/intel/ixp425/ixp425 here are the gpio defs...
My thought is that gpio is linearly above gpio[1]... so I am going to add it... :)
Here is the section of the boundary scan register defs in the file...

bit 385 C ? .
bit 384 B ? GPIO[1] 369 1 Z
bit 383 B ? GPIO[2] 368 1 Z
bit 382 B ? GPIO[3] 367 1 Z
bit 381 B ? GPIO[4] 366 1 Z
bit 380 B ? GPIO[5] 365 1 Z
bit 379 B ? GPIO[6] 364 1 Z
bit 378 B ? GPIO[7] 363 1 Z
bit 377 B ? GPIO[8] 362 1 Z
bit 376 B ? GPIO[9] 361 1 Z
bit 375 B ? GPIO[10] 360 1 Z
bit 374 B ? GPIO[11] 359 1 Z
bit 373 B ? GPIO[12] 358 1 Z
bit 372 B ? GPIO[13] 357 1 Z
bit 371 B ? GPIO[14] 356 1 Z
bit 370 B ? GPIO[15] 355 1 Z
bit 369 C ? .
bit 368 C ? .
bit 367 C ? .