By cross-checking STMPE 610/801/811/1601/2401/2403 datasheets,
it appears that edge detection and rising/falling edge detection
is not supported by all STMPE variant:

           GPIO              GPIO
      Edge detection     rising/falling
                         edge detection
 610 |      X        |         X       |
 801 |               |                 |
 811 |      X        |         X       |
1600 |               |                 |
1601 |      X        |         X       |
1801 |               |         X       |
2401 |      X        |         X       |
2403 |      X        |         X       |

Rework stmpe_dbg_show_one() and stmpe_gpio_irq to correctly
take these cases into account.
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>