Add ILI9341 TFT driver (SPI) for ATSAMD2x

[sago35]

No description provided.

[sago35]

I haven't added the pyportal_boring setting because 32KB of memory is not enough.

$ tinygo flash -target xiao -size short ./examples/ili9341/basic/
   code    data     bss |   flash     ram
  11716       8    4300 |   11724    4308

$ tinygo flash -target xiao -size short ./examples/ili9341/scroll/
   code    data     bss |   flash     ram
  11780       8    4300 |   11788    4308

$ tinygo flash -target xiao -size short ./examples/ili9341/pyportal_boing/
tinygo:ld.lld: error: section '.bss' will not fit in region 'RAM': overflowed by 2717 bytes
tinygo:ld.lld: error: section '.bss' will not fit in region 'RAM': overflowed by 2720 bytes
tinygo:ld.lld: error: section '.bss' will not fit in region 'RAM': overflowed by 2717 bytes
tinygo:ld.lld: error: section '.bss' will not fit in region 'RAM': overflowed by 2720 bytes
tinygo:ld.lld: error: section '.bss' will not fit in region 'RAM': overflowed by 2717 bytes
tinygo:ld.lld: error: section '.bss' will not fit in region 'RAM': overflowed by 2720 bytes
failed to run tool: ld.lld
error: failed to link /tmp/tinygo178178479/main: exit status 1

I rewrote targets/atsamd21.ld to check for memory requirements and found the following became
pyprotal_boing won't work unless you split the frame_buffer or make other changes.

$ tinygo build -o app.elf -target xiao -size full ./examples/ili9341/pyportal_boing/
   code  rodata    data     bss |   flash     ram | package
   4356      13       0       0 |    4369       0 | (bootstrap)
      0      36       0       0 |      36       0 | handleHardFault$string
    100      24       0       4 |     124       4 | internal/task
   3252      50       5    2054 |    3307    2059 | machine
      0      16       0     130 |      16     130 | machine$alloc
   2698      97       0      33 |    2795      33 | runtime
    216       0       0       0 |     216       0 | time
   2680   16463       0   31175 |   19143   31175 | tinygo
  13302   16699       5   33396 |   30006   33401 | (sum)
  30296       -       8   35472 |   30304   35480 | (all)

[deadprogram]

I do not have the hardware myself to test this, but looks good to me @sago35 thank you for working on this.

Now squash/merging.