phosphor-fan: Change fan-presence dep to .wants

Change the dependency that the fan presence application has on the power
on target to a wants instead of requires so it doesn't power off the
system if it were to go into a failed state with power on.

Signed-off-by: Matt Spinler <spinler@us.ibm.com>
Change-Id: I460a6cfd51a0bc46503168151d9f4e3b17264b80
diff --git a/meta-phosphor/recipes-phosphor/fans/phosphor-fan_git.bb b/meta-phosphor/recipes-phosphor/fans/phosphor-fan_git.bb
index 9540c8b..cc3d64f 100644
--- a/meta-phosphor/recipes-phosphor/fans/phosphor-fan_git.bb
+++ b/meta-phosphor/recipes-phosphor/fans/phosphor-fan_git.bb
@@ -57,7 +57,7 @@
 TMPL_TACH = "phosphor-fan-presence-tach@.service"
 INSTFMT_TACH = "phosphor-fan-presence-tach@{0}.service"
 POWERON_TGT = "obmc-chassis-poweron@{0}.target"
-FMT_TACH = "../${TMPL_TACH}:${POWERON_TGT}.requires/${INSTFMT_TACH}"
+FMT_TACH = "../${TMPL_TACH}:${POWERON_TGT}.wants/${INSTFMT_TACH}"
 FMT_TACH_MUSR = "../${TMPL_TACH}:${MULTI_USR_TGT}.wants/${INSTFMT_TACH}"
 
 FILES:${PN}-presence-tach = "${bindir}/phosphor-fan-presence-tach"