Config option to enable PHAL APIs

There are a couple required PHAL APIs that are not available upstream.
It is uncertain if these APIs will ever be available upstream.
Fortunately, the APIs are only needed to provide information that is
displayed in a PEL. So there is a less accuate alternative when the APIs
are not available.

Change-Id: I1a4a1838520c18053ab31f561d05875d4a94c20e
Signed-off-by: Zane Shelley <zshelle@us.ibm.com>
diff --git a/meson_options.txt b/meson_options.txt
index b1c8b8f..635fb07 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -1,2 +1,7 @@
 option('tests', type: 'feature', description: 'Build tests')
 option('nlmode', type: 'feature', description: 'no run-time control')
+
+option('phal', type: 'feature', value : 'disabled',
+        description : '''Enable PHAL APIs for retrieving data from the POWER
+                         Systems device tree''')
+