of: unittest: print pass messages at PR_INFO level

Printing the devicetree unittest pass message for each passed test
creates much console verbosity.  The existing pass messages are
printed at loglevel KERN_DEBUG so they will not print by default.

Change default to print the pass messages at loglevel PR_INFO so
they will print with the default console loglevel.

The test community expects either a pass or a fail message for each
test in a test suite.  The messages are typically post-processed to
report pass/fail results.

Signed-off-by: Frank Rowand <frank.rowand@sony.com>
Tested-by: Linux Kernel Functional Testing <lkft@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220210230819.3303212-1-frowand.list@gmail.com