test: Move help into the suite declaration

test: Move help into the suite declaration

Rather than having the help in the longhelp, put it in the suite info
so 'ut info -s' can show it. This is tidier, particular due to the
removal of #ifdefs

This means that the help text is present in the image (although not
displayed with 'ut info -s') so the image-size increases. But with
UNIT_TEST enabled, we expect large images so this doesn't seem
important.

Signed-off-by: Simon Glass <sjg@chromium.org>