UefiCpuPkg: 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
UefiCpuPkg.

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: Ray Ni <ray.ni@intel.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>

UefiCpuPkg/Library/BaseRiscV64CpuExceptionHandlerLib/CpuExceptionHandlerLib.c

@@ -230,7 +230,7 @@ RegisterCpuInterruptHandler (
   IN EFI_CPU_INTERRUPT_HANDLER  InterruptHandler
   )
 {
-  DEBUG ((DEBUG_INFO, "%a: Type:%x Handler: %x\n", __FUNCTION__, ExceptionType, InterruptHandler));
+  DEBUG ((DEBUG_INFO, "%a: Type:%x Handler: %x\n", __func__, ExceptionType, InterruptHandler));
   if (EXCEPT_RISCV_IS_IRQ (ExceptionType)) {
     if (EXCEPT_RISCV_IRQ_INDEX (ExceptionType) > EXCEPT_RISCV_MAX_IRQS) {
       return EFI_UNSUPPORTED;