ish: don't specify any on-board tests
ish: don't specify any on-board tests

We have no framework to do on-board testing on ish. The make target
should do nothing.

BUG=b:134446400
BRANCH=none
TEST="make BOARD=arcada_ish tests" does nothing

Change-Id: Ic71b35a24d37f7b827f6639669c6d43659cda06e
Signed-off-by: Jack Rosenthal <d3f605bef1867f59845d4ce6e4f83b8dc9e4e0ae@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1643834
Reviewed-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec