meson: Reduce strength of oem-ibm requirements from enabled to allowed

If it's not expressly disabled, do what's necessary to build the oem-ibm
pieces of the code-base. Capture the newly-enabled APIs in the ABI
dumps.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I50168309432620e03f00a4620b6bfc38f2e575c8
diff --git a/src/meson.build b/src/meson.build
index 42193c9..3506113 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -12,6 +12,6 @@
 subdir('requester')
 subdir('transport')
 
-if get_option('oem-ibm').enabled()
+if get_option('oem-ibm').allowed()
    subdir('oem/ibm')
 endif