meta-phosphor: change systemd.bbclass to match upstream override syntax

Upstream bbclasses changed to typically use the `:${PN}` override
syntax, including the SYSTEMD_ variables.  Change our systemd.bbclass
to do the same for consistency and perform a tree-wide variable
replacement.

Spot checked by building bletchley and witherspoon and checking
some of the SYSTEMD_LINK directives on installed packages under qemu.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I20a9dd809bff8af8759488734f80486c7228c6eb
diff --git a/meta-inspur/meta-fp5280g2/recipes-phosphor/fans/phosphor-fan_%.bbappend b/meta-inspur/meta-fp5280g2/recipes-phosphor/fans/phosphor-fan_%.bbappend
index 319cd16..79a13f6 100644
--- a/meta-inspur/meta-fp5280g2/recipes-phosphor/fans/phosphor-fan_%.bbappend
+++ b/meta-inspur/meta-fp5280g2/recipes-phosphor/fans/phosphor-fan_%.bbappend
@@ -14,8 +14,8 @@
 
 FILES:phosphor-cooling-type = "${bindir}/phosphor-cooling-type"
 SYSTEMD_SERVICE:phosphor-cooling-type += "${TMPL_COOLING}"
-SYSTEMD_LINK_phosphor-cooling-type += "${@compose_list(d, 'FMT_COOLING', 'OBMC_CHASSIS_INSTANCES')}"
+SYSTEMD_LINK:phosphor-cooling-type += "${@compose_list(d, 'FMT_COOLING', 'OBMC_CHASSIS_INSTANCES')}"
 
 COOLING_ENV_FMT = "obmc/phosphor-fan/phosphor-cooling-type-{0}.conf"
 
-SYSTEMD_ENVIRONMENT_FILE_phosphor-cooling-type:append:fp5280g2 = " ${@compose_list(d, 'COOLING_ENV_FMT', 'OBMC_CHASSIS_INSTANCES')}"
+SYSTEMD_ENVIRONMENT_FILE:phosphor-cooling-type:append:fp5280g2 = " ${@compose_list(d, 'COOLING_ENV_FMT', 'OBMC_CHASSIS_INSTANCES')}"