samples: display: Limit lvgl sample execution to boards with shield

Similar to commit c6ff61220e8af1c444d0d23210830c5131cd53b3, use a
harness config to limit execution of the adafruit_2_8_tft_touch_v2
sample variant to boards that have this shield attached.

Signed-off-by: Maureen Helm <maureen.helm@nxp.com>
1 file changed