x86, paravirt: fix build error when thp is disabled

With CONFIG_PARAVIRT=y and CONFIG_TRANSPARENT_HUGEPAGE=n, the build breaks
because set_pmd_at() is undeclared:

  mm/memory.c: In function 'do_pmd_numa_page':
  mm/memory.c:3520: error: implicit declaration of function 'set_pmd_at'
  mm/mprotect.c: In function 'change_pmd_protnuma':
  mm/mprotect.c:120: error: implicit declaration of function 'set_pmd_at'

This is because paravirt defines set_pmd_at() only when
CONFIG_TRANSPARENT_HUGEPAGE=y and such a restriction is unneeded.  The
fix is to define it for all CONFIG_PARAVIRT configurations.
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/include/asm/paravirt.h

@@ -528,7 +528,6 @@ static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 		PVOP_VCALL4(pv_mmu_ops.set_pte_at, mm, addr, ptep, pte.pte);
 }
 
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
 static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 			      pmd_t *pmdp, pmd_t pmd)
 {
@@ -539,7 +538,6 @@ static inline void set_pmd_at(struct mm_struct *mm, unsigned long addr,
 		PVOP_VCALL4(pv_mmu_ops.set_pmd_at, mm, addr, pmdp,
 			    native_pmd_val(pmd));
 }
-#endif
 
 static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
 {