arm64: Update Documentation/arm references

The Arm documentation has moved to Documentation/arch/arm; update
references under arch/arm64 to match.

Cc: Will Deacon <will@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

arch/arm64/Kconfig

@@ -1619,7 +1619,7 @@ config KUSER_HELPERS
 	  the system. This permits binaries to be run on ARMv4 through
 	  to ARMv8 without modification.
 
-	  See Documentation/arm/kernel_user_helpers.rst for details.
+	  See Documentation/arch/arm/kernel_user_helpers.rst for details.
 
 	  However, the fixed address nature of these helpers can be used
 	  by ROP (return orientated programming) authors when creating

arch/arm64/kernel/kuser32.S

@@ -10,7 +10,7 @@
  * aarch32_setup_additional_pages() and are provided for compatibility
  * reasons with 32 bit (aarch32) applications that need them.
  *
- * See Documentation/arm/kernel_user_helpers.rst for formal definitions.
+ * See Documentation/arch/arm/kernel_user_helpers.rst for formal definitions.
  */
 
 #include <asm/unistd.h>