phosphor-debug-collector: Fix invalied escape sequence

There is a warning message in the phosphor-debug-collector repo when
using bitbake to build image-bmc:
DeprecationWarning: invalid escape sequence \W
   config_values = re.split('\W+', parse_value, 1)

The reason is that `\W` is regarded as an escaped character,
add `r` to fix it.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I59836e7df9a73a01d47cd03e916f0ab1b8c2d716