regulators: Implement ComparePresenceAction class

The ComparePresenceAction::execute() method reads the presence value
using the Services->getPresenceService()->isPresent() method.
Then it compares the actual value to the expected value.
It returns true if they match and false if they don't.

Signed-off-by: Bob King <Bob_King@wistron.com>
Change-Id: Ie6a17191313b2c80a0ecd7a7d7357448985d0673
diff --git a/phosphor-regulators/src/meson.build b/phosphor-regulators/src/meson.build
index bfcacb1..8238d93 100644
--- a/phosphor-regulators/src/meson.build
+++ b/phosphor-regulators/src/meson.build
@@ -21,6 +21,7 @@
     'system.cpp',
     'temporary_file.cpp',
 
+    'actions/compare_presence_action.cpp',
     'actions/if_action.cpp',
     'actions/i2c_compare_bit_action.cpp',
     'actions/i2c_compare_byte_action.cpp',