uboot-imx

tools: Update python "help" tests to cope with "more" oddities

In some cases when "more" is told to page a given file it will prepend
the output with:
::::::::::::::
/PATH/TO/THE/FILE
::::::::::::::

And when this happens the output will not match the expected length.
Further, if we use a different pager we will instead fail the coverage
tests as we will not have 100% coverage.  Update the help test to remove
the string in question.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Tom Rini <trini@konsulko.com>