docs: fix broken documentation links

Mostly due to x86 and acpi conversion, several documentation
links are still pointing to the old file. Fix them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Reviewed-by: Wolfram Sang <wsa@the-dreams.de>
Reviewed-by: Sven Van Asbroeck <TheSven73@gmail.com>
Reviewed-by: Bhupesh Sharma <bhsharma@redhat.com>
Acked-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

arch/x86/include/asm/bootparam_utils.h

@@ -24,7 +24,7 @@ static void sanitize_boot_params(struct boot_params *boot_params)
 	 * IMPORTANT NOTE TO BOOTLOADER AUTHORS: do not simply clear
 	 * this field.  The purpose of this field is to guarantee
 	 * compliance with the x86 boot spec located in
-	 * Documentation/x86/boot.txt .  That spec says that the
+	 * Documentation/x86/boot.rst .  That spec says that the
 	 * *whole* structure should be cleared, after which only the
 	 * portion defined by struct setup_header (boot_params->hdr)
 	 * should be copied in.

arch/x86/include/asm/page_64_types.h

@@ -48,7 +48,7 @@
 
 #define __START_KERNEL_map	_AC(0xffffffff80000000, UL)
 
-/* See Documentation/x86/x86_64/mm.txt for a description of the memory map. */
+/* See Documentation/x86/x86_64/mm.rst for a description of the memory map. */
 
 #define __PHYSICAL_MASK_SHIFT	52
 

arch/x86/include/asm/pgtable_64_types.h

@@ -103,7 +103,7 @@ extern unsigned int ptrs_per_p4d;
 #define PGDIR_MASK	(~(PGDIR_SIZE - 1))
 
 /*
- * See Documentation/x86/x86_64/mm.txt for a description of the memory map.
+ * See Documentation/x86/x86_64/mm.rst for a description of the memory map.
  *
  * Be very careful vs. KASLR when changing anything here. The KASLR address
  * range must not overlap with anything except the KASAN shadow area, which