ManageabilityPkg: Declare variadic function with EFIAPI

HelperManageabilityDebugPrint() is a variadic function that is not
declared with EFIAPI, leading to a compiler failure when building with
CLANGDWARF:

  BaseManageabilityTransportHelper.c:462:3: error:
    '__builtin_ms_va_start' used in System V ABI function

While other functions in the header should also use EFIAPI, this
commit is making a minimal change to fix CI from failing for every
commit to master.

Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>

ManageabilityPkg/Include/Library/ManageabilityTransportHelperLib.h

diff --git a/ManageabilityPkg/Include/Library/ManageabilityTransportHelperLib.h b/ManageabilityPkg/Include/Library/ManageabilityTransportHelperLib.h
index 6c07452..43852e1 100644
--- a/ManageabilityPkg/Include/Library/ManageabilityTransportHelperLib.h
+++ b/ManageabilityPkg/Include/Library/ManageabilityTransportHelperLib.h
@@ -180,6 +180,7 @@
 

 **/

 VOID

+EFIAPI

 HelperManageabilityDebugPrint (

   IN  VOID         *Payload,

   IN  UINT32       PayloadSize,

ManageabilityPkg/Library/BaseManageabilityTransportHelperLib/BaseManageabilityTransportHelper.c

diff --git a/ManageabilityPkg/Library/BaseManageabilityTransportHelperLib/BaseManageabilityTransportHelper.c b/ManageabilityPkg/Library/BaseManageabilityTransportHelperLib/BaseManageabilityTransportHelper.c
index b097a8a..e4d16fa 100644
--- a/ManageabilityPkg/Library/BaseManageabilityTransportHelperLib/BaseManageabilityTransportHelper.c
+++ b/ManageabilityPkg/Library/BaseManageabilityTransportHelperLib/BaseManageabilityTransportHelper.c
@@ -450,6 +450,7 @@
 

 **/

 VOID

+EFIAPI

 HelperManageabilityDebugPrint (

   IN  VOID         *Payload,

   IN  UINT32       PayloadSize,