meson: simplify dependencies

Leverage wrapfile `[provide]` directives to simplify the dependency
searching in the meson.build.

Change-Id: I01c308089b1b6586f552a10cbcd0641faec4ae26
diff --git a/subprojects/sdeventplus.wrap b/subprojects/sdeventplus.wrap
index 085bb5e..f871ac0 100644
--- a/subprojects/sdeventplus.wrap
+++ b/subprojects/sdeventplus.wrap
@@ -1,3 +1,6 @@
 [wrap-git]
 url = https://github.com/openbmc/sdeventplus.git
 revision = HEAD
+
+[provide]
+sdeventplus = sdeventplus_dep