x86/kexec: Fix a comment of swap_pages() assembly

When relocate_kernel() gets called, %rdi holds 'indirection_page' and
%rsi holds 'page_list'.  And %rdi always holds 'indirection_page' when
swap_pages() is called.

Therefore the comment of the first line code of swap_pages()

	movq    %rdi, %rcx      /* Put the page_list in %rcx */

.. isn't correct because it actually moves the 'indirection_page' to
the %rcx.  Fix it.
Signed-off-by: Kai Huang <kai.huang@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Link: https://lore.kernel.org/all/adafdfb1421c88efce04420fc9a996c0e2ca1b34.1724573384.git.kai.huang@intel.com

arch/x86/kernel/relocate_kernel_64.S

@@ -258,7 +258,7 @@ SYM_CODE_END(virtual_mapped)
 	/* Do the copies */
 SYM_CODE_START_LOCAL_NOALIGN(swap_pages)
 	UNWIND_HINT_END_OF_STACK
-	movq	%rdi, %rcx	/* Put the page_list in %rcx */
+	movq	%rdi, %rcx	/* Put the indirection_page in %rcx */
 	xorl	%edi, %edi
 	xorl	%esi, %esi
 	jmp	1f