PEL: Point to libpldm repo in subproject

PLDM split into two repositories, so point at the one that is actually
needed as a subproject.  Also remove a PLDM meson option that isn't used
anymore.

Change-Id: I79d4084d9dc6260dc1a0915f679d429f3c81792e
Signed-off-by: Matt Spinler <spinler@us.ibm.com>
diff --git a/subprojects/libpldm.wrap b/subprojects/libpldm.wrap
new file mode 100644
index 0000000..5c90142
--- /dev/null
+++ b/subprojects/libpldm.wrap
@@ -0,0 +1,6 @@
+[wrap-git]
+url = https://github.com/openbmc/libpldm.git
+revision = HEAD
+
+[provide]
+libpldm = libpldm_dep