meta-phosphor: eliminate OBMC_POWER_INSTANCES

In no currently available systems is there an instance where the "power
instance" is separate from the "chassis instance".  Simplify the
systemd target linkages by removing this variable.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I847804e2328cc20c228f05895448ef3170dfbc8a
diff --git a/meta-phosphor/recipes-phosphor/state/phosphor-state-manager_git.bb b/meta-phosphor/recipes-phosphor/state/phosphor-state-manager_git.bb
index be94e2d..fce5fdd 100644
--- a/meta-phosphor/recipes-phosphor/state/phosphor-state-manager_git.bb
+++ b/meta-phosphor/recipes-phosphor/state/phosphor-state-manager_git.bb
@@ -234,7 +234,7 @@
 START_TGTFMT_CTRL = "obmc-host-startmin@{1}.target"
 START_INSTFMT_CTRL = "obmc-chassis-poweron@{0}.target"
 START_FMT_CTRL = "../${START_TMPL_CTRL}:${START_TGTFMT_CTRL}.requires/${START_INSTFMT_CTRL}"
-SYSTEMD_LINK:${PN}-obmc-targets += "${@compose_list_zip(d, 'START_FMT_CTRL', 'OBMC_POWER_INSTANCES', 'OBMC_CHASSIS_INSTANCES')}"
+SYSTEMD_LINK:${PN}-obmc-targets += "${@compose_list_zip(d, 'START_FMT_CTRL', 'OBMC_CHASSIS_INSTANCES', 'OBMC_CHASSIS_INSTANCES')}"
 
 # Chassis off requires host off
 STOP_TMPL_CTRL = "obmc-host-stop@.target"