Re: dtc: Don't delete *.test.dtb between testgroups

So, like, the other day David Gibson mumbled:

The dtc/libfdt testsuite creates a number of .dtb files during its
run.  To ensure a clean test run, these are currently deleted before
each group of tests.

This is, in fact, a mistake, since if something goes wrong in the
first group of tests, deleting the .dtb at the beginning of the second
group of tests makes it harder to figure out what the problem was.

This patch changes the script to only delete the files once, before
the whole test run.

Signed-off-by: David Gibson <redacted>

Applied.

jdl