OvmfPkg: Update code to be more C11 compliant by using __func__

__FUNCTION__ is a pre-standard extension that gcc and Visual C++ among
others support, while __func__ was standardized in C99.

Since it's more standard, replace __FUNCTION__ with __func__ throughout
OvmfPkg.

Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Reviewed-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

OvmfPkg/VirtioFsDxe/FuseLookup.c

@@ -128,7 +128,7 @@ VirtioFsFuseLookup (
          DEBUG_VERBOSE :
          DEBUG_ERROR),
         "%a: Label=\"%s\" DirNodeId=%Lu Name=\"%a\" Errno=%d\n",
-        __FUNCTION__,
+        __func__,
         VirtioFs->Label,
         DirNodeId,
         Name,