AP_ToshibaCAN: remove support

[rmackay9]

This removes support for the ToshibaCAN ESCs (see wiki here).

Toshiba has discontinued these ESCs and we never really saw much uptake from the community so I don't think there are any active users of them. I've checked with EAMS Robotics (the sponsor of the original development) and they've also confirmed that they're no longer using them and it is OK from their point of view to remove support.

[amilcarlucas]

Binary Name      Text [B]          Data [B]     BSS (B)       Total Flash Change [B] (%)      Flash Free After PR (B)
---------------  ----------------  -----------  ------------  ----------------------------  -------------------------
arducopter-heli  -3472 (-0.1961%)  0 (0.0000%)  0 (0.0000%)   -3472 (-0.1958%)                                 196096
ardurover        -3484 (-0.2193%)  0 (0.0000%)  4 (+0.0015%)  -3484 (-0.2190%)                                 378944
arduplane        -3472 (-0.1991%)  0 (0.0000%)  0 (0.0000%)   -3472 (-0.1987%)                                 222224
blimp            -248 (-0.0192%)   0 (0.0000%)  0 (0.0000%)   -248 (-0.0192%)                                  674484
arducopter       -3832 (-0.2174%)  0 (0.0000%)  0 (0.0000%)   -3832 (-0.2170%)                                 204112
antennatracker   -3484 (-0.2581%)  0 (0.0000%)  4 (+0.0015%)  -3484 (-0.2577%)                                 617696
ardusub          -3472 (-0.2240%)  0 (0.0000%)  0 (0.0000%)   -3472 (-0.2237%)                                 417340