Add power supply derating factor to meson options

Add the option to specify the power supply derating factor.

Signed-off-by: Eddie James <eajames@linux.ibm.com>
Change-Id: Ibfbb52f64c5b9133fbbc8cbb267aa9618c079cc6
diff --git a/meson.build b/meson.build
index 0bb8aee..daf1c15 100644
--- a/meson.build
+++ b/meson.build
@@ -23,7 +23,7 @@
 conf_data.set('MAX_CPUS', get_option('max-cpus'))
 conf_data.set('OCC_CPU_TEMP_SENSOR_TYPE', 0xC0)
 conf_data.set('OCC_DIMM_TEMP_SENSOR_TYPE', 0xD0)
-conf_data.set('PS_DERATING_FACTOR', 90)
+conf_data.set('PS_DERATING_FACTOR', get_option('ps-derating-factor'))
 
 if get_option('i2c-occ').enabled()
     conf_data.set_quoted('OCC_HWMON_PATH', '/sys/bus/i2c/drivers/occ-hwmon/')