meson: adjust nlohmann-json dependency

Simplify the meson directive for nlohmann-json dependency and rename the
wrap file to align with other repositories.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I6ad9d4fe3e8fa24673b736bab81e2fcabc51f1a0
diff --git a/extensions/openpower-pels/meson.build b/extensions/openpower-pels/meson.build
index 1cf9839..f1c10f1 100644
--- a/extensions/openpower-pels/meson.build
+++ b/extensions/openpower-pels/meson.build
@@ -3,11 +3,7 @@
     default_options: ['oem-ibm=enabled'],
 )
 
-if cpp.has_header('nlohmann/json.hpp')
-    nlohmann_json_dep = declare_dependency()
-else
-    nlohmann_json_dep = dependency('nlohmann-json')
-endif
+nlohmann_json_dep = dependency('nlohmann_json', include_type: 'system')
 
 python_inst = import('python').find_installation('python3')
 python_ver = python_inst.language_version()
diff --git a/subprojects/nlohmann-json.wrap b/subprojects/nlohmann-json.wrap
deleted file mode 100644
index a2884b1..0000000
--- a/subprojects/nlohmann-json.wrap
+++ /dev/null
@@ -1,6 +0,0 @@
-[wrap-git]
-url = https://github.com/nlohmann/json
-revision = HEAD
-
-[provide]
-nlohmann-json = nlohmann_json_dep
diff --git a/subprojects/nlohmann_json.wrap b/subprojects/nlohmann_json.wrap
new file mode 100644
index 0000000..3745380
--- /dev/null
+++ b/subprojects/nlohmann_json.wrap
@@ -0,0 +1,6 @@
+[wrap-git]
+revision = HEAD
+url = https://github.com/nlohmann/json.git
+
+[provide]
+nlohmann_json = nlohmann_json_dep