xen/ppc: Fix double xen_ulong_t typedef in public/arch-ppc.h

public/arch-ppc.h contains two adjacent #ifndef __ASSEMBLY__ blocks.

With these merged, it becomes very obvious that there's a duplicate
definition of xen_ulong_t, which is also noticed by the docs build:

  /usr/bin/perl -w /local/xen.git/docs/xen-headers -O html/hypercall/ppc \
          -T 'arch-ppc - Xen public headers' \
          -X arch-arm -X arch-riscv -X arch-x86_32 -X arch-x86_64 \
          -X xen-arm -X xen-riscv -X xen-x86_32 -X xen-x86_64 \
          -X arch-x86 \
          /local/xen.git/docs/../xen include/public include/xen/errno.h
  include/public/memory.h:63: multiple definitions of Typedef xen_ulong_t: include/public/arch-ppc.h:55
  include/public/memory.h:63: multiple definitions of Typedef xen_ulong_t: include/public/arch-ppc.h:61
  include/public/memory.h:63: multiple definitions of Typedef xen_ulong_t: include/public/arch-ppc.h:61
  include/public/memory.h:63: multiple definitions of Typedef xen_ulong_t: include/public/arch-ppc.h:55

Drop the second typedef.  Finally, annotate the #endif so it's clear
what it refers to.

Fixes: 08c192cc11 ("xen/ppc: Add public/arch-ppc.h")
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Shawn Anastasio <sanastasio@raptorengineering.com>

xen/include/public/arch-ppc.h

@@ -54,11 +54,6 @@ typedef uint64_t xen_pfn_t;
 
 typedef uint64_t xen_ulong_t;
 #define PRI_xen_ulong PRIx64
-#endif
-
-#ifndef __ASSEMBLY__
-
-typedef uint64_t xen_ulong_t;
 
 /*
  * User-accessible registers: most of these need to be saved/restored
@@ -107,6 +102,6 @@ struct xen_arch_domainconfig {
 
 typedef struct xen_pmu_arch { uint8_t dummy; } xen_pmu_arch_t;
 
-#endif
+#endif /* !__ASSEMBLY__ */
 
 #endif /* __XEN_PUBLIC_ARCH_PPC_H__ */