x86/mm: Drop unneeded __always_inline for p4d page table helpers

This reverts the following commits:

  1ea66554d3 ("x86/mm: Mark p4d_offset() __always_inline")
  046c0dbec0 ("x86: Mark native_set_p4d() as __always_inline")

p4d_offset(), native_set_p4d() and native_p4d_clear() were marked
__always_inline in attempt to move __pgtable_l5_enabled into __initdata
section.

It was required as KASAN initialization code is a user of
USE_EARLY_PGTABLE_L5, so all pgtable_l5_enabled() translated to
__pgtable_l5_enabled there. This includes pgtable_l5_enabled() called
from inline p4d helpers.

If compiler would decided to not inline these p4d helpers, but leave
them standalone, we end up with section mismatch.

We don't need __always_inline here anymore. __pgtable_l5_enabled moved
back to be __ro_after_init. See the following commit:

  51be133515 ("Revert "x86/mm: Mark __pgtable_l5_enabled __initdata"")

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20180626100341.49910-1-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/pgtable.h

@@ -898,7 +898,7 @@ static inline unsigned long pgd_page_vaddr(pgd_t pgd)
 #define pgd_page(pgd)	pfn_to_page(pgd_pfn(pgd))
 
 /* to find an entry in a page-table-directory. */
-static __always_inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)
+static inline p4d_t *p4d_offset(pgd_t *pgd, unsigned long address)
 {
 	if (!pgtable_l5_enabled())
 		return (p4d_t *)pgd;

arch/x86/include/asm/pgtable_64.h

@@ -216,7 +216,7 @@ static inline pgd_t pti_set_user_pgd(pgd_t *pgdp, pgd_t pgd)
 }
 #endif
 
-static __always_inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
+static inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
 {
 	pgd_t pgd;
 
@@ -230,7 +230,7 @@ static __always_inline void native_set_p4d(p4d_t *p4dp, p4d_t p4d)
 	*p4dp = native_make_p4d(native_pgd_val(pgd));
 }
 
-static __always_inline void native_p4d_clear(p4d_t *p4d)
+static inline void native_p4d_clear(p4d_t *p4d)
 {
 	native_set_p4d(p4d, native_make_p4d(0));
 }