common: move asyncSystem() to common

asyncSystem() is shared across updaters, so moved to common.

Change-Id: I3545d34ecc1f1bf8a226d020267ae00bcf42c5f9
Signed-off-by: Kevin Tung <Kevin.Tung@quantatw.com>
diff --git a/bios/spi_device.hpp b/bios/spi_device.hpp
index 25a53d1..63e7956 100644
--- a/bios/spi_device.hpp
+++ b/bios/spi_device.hpp
@@ -110,8 +110,8 @@
     // Intel Flash Descriptor
     // @param image           the component image
     // @param image_size      size of 'image'
-    // @returns               0 on success
-    sdbusplus::async::task<int> writeSPIFlashWithFlashrom(
+    // @returns               true on success
+    sdbusplus::async::task<bool> writeSPIFlashWithFlashrom(
         const uint8_t* image, size_t image_size) const;
 
     // @description preconditions: