meta-romulus: Add fan monitor config

1. Enable fan monitor;
2. Add FanPwm interface;
3. Set the factor, offset for calculation from pwm to rpm

Tested: Verifid fan monitor works fine;
        Manually change pwm, fan monitor will set fan non-functional
        after a while; change pwm back, it will set fan functional
        again, as expected.

Change-Id: Ic56cbe291959368218b60c4a5b8e305f39ff7edb
Signed-off-by: Lei YU <mine260309@gmail.com>
diff --git a/meta-romulus/recipes-phosphor/fans/phosphor-fan-monitor-config-native.bbappend b/meta-romulus/recipes-phosphor/fans/phosphor-fan-monitor-config-native.bbappend
new file mode 100644
index 0000000..72d991c
--- /dev/null
+++ b/meta-romulus/recipes-phosphor/fans/phosphor-fan-monitor-config-native.bbappend
@@ -0,0 +1 @@
+FILESEXTRAPATHS_prepend := "${THISDIR}/${PN}:"