phosphor-hwmon-config-mrw: avoid relative path in recipe

This path can be different on different build systems.
Instead, use WORKDIR as the path.

Change-Id: I11f91087c62174e1f700c7c7d7d4618a4c0b47df
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/classes/mrw-rev.bbclass b/classes/mrw-rev.bbclass
index 7cf8e7d..9a49bd4 100644
--- a/classes/mrw-rev.bbclass
+++ b/classes/mrw-rev.bbclass
@@ -2,4 +2,4 @@
 MRW_API_SRCREV ?= "60c8e10cbb11768cd1ba394b35cb1d6627efec42"
 
 MRW_TOOLS_SRC_URI ?= "git://github.com/openbmc/phosphor-mrw-tools"
-MRW_TOOLS_SRCREV ?= "902c85375105db9f73353f510b4a6e2651d65c9e"
+MRW_TOOLS_SRCREV ?= "9142da4b410e6c34aca3ef8a8e84b13d39a9c00d"